Are you tired of seeing the dreaded ERROR_91 pop up on your Windows PC? Don’t worry — you’re not alone, and more importantly, this error is fixable! ERROR_91 commonly occurs when a program tries to use an object variable that hasn’t been set or initialized, leading to frustrating crashes or software hiccups. Whether you see this error in Excel macros, VBScript, or other Windows applications, this comprehensive step-by-step guide will help you diagnose and resolve ERROR_91 like a pro.
What Is ERROR_91 in Windows?
ERROR_91: “Object variable or With block variable not set” typically occurs in VBA (Visual Basic for Applications), VBScript, or programs run on Windows when the system expects an object to be assigned but finds it empty or uninitialized.
This can happen due to:
- Missing or corrupted object references
- Faulty scripts or macros
- Improper application settings
- Conflicts or bugs in software
Understanding the root cause will help you troubleshoot effectively.
Step 1: Identify When and Where ERROR_91 Occurs
The first step to fixing ERROR_91 is pinpointing which program or process causes it.
- Does it occur during a specific task (e.g., running an Excel macro)?
- Is it consistent or intermittent?
- Note the exact error message and the program involved.
Documenting these details will guide the troubleshooting steps ahead.
Step 2: Restart Your PC and Close Background Applications
Although it sounds basic, many issues resolve by simply restarting your computer.
- Save your work and restart Windows.
- Close unnecessary background programs to reduce conflicts.
- Try replicating the action that caused ERROR_91 to see if it persists.
If the error continues, move on to the next steps.
Step 3: Check and Debug the Script or Macro (For Developers or Advanced Users)
If ERROR_91 appears when running VBA macros or VBScript, the issue likely lies in the code trying to use an uninitialized object.
How to debug:
- Open the macro or script editor (for example, press
Alt + F11in Excel to open the VBA editor). - Find the line causing the error — it’s usually highlighted when the error pops up.
- Ensure all object variables are properly set before use.
Example:
vba
Dim ws as Worksheet
Set ws = ThisWorkbook.Sheets("Sheet1") ‘ Make sure to Set the object
‘ Without Set, attempting to access ws will cause ERROR_91
- Add error handling to trap unexpected issues:
vba
On Error Resume Next
‘ Your code here
On Error GoTo 0
If you aren’t comfortable editing code, contact the software provider or a developer.
Step 4: Repair or Reinstall the Program
Corrupted program files can trigger ERROR_91 repeatedly.
- Go to Control Panel > Programs > Programs and Features.
- Find the application showing the error.
- Choose Repair if available. If not,
- Uninstall and then reinstall the application from a trusted source.
This often fixes missing or damaged files causing the problem.
Step 5: Update Windows and Software
Outdated operating systems or applications may contain bugs responsible for the error.
-
Update Windows:
- Go to Settings > Update & Security > Windows Update
- Click Check for updates and install any pending updates.
- Update the application that produces ERROR_91 to the latest version.
Keeping software current addresses known bugs and improves stability.
Step 6: Check for Missing or Incorrect Object References
In VBA or scripting environments, references to external libraries or objects must be correct.
How to verify references in VBA:
- Open the VBA editor (
Alt + F11). - Go to Tools > References.
- Look for any “Missing” references and uncheck them.
- Re-add the correct libraries if needed.
Incorrect references can lead to ERROR_91 when a required object isn’t found.
Step 7: Scan for Malware and System File Corruption
Malware or corrupted system files can disrupt normal operation.
- Run a full system scan with Windows Defender or trusted antivirus software.
-
Use System File Checker (SFC) to repair corrupted files:
- Open Command Prompt as Administrator.
- Type
sfc /scannowand press Enter. - Wait for the process to complete and apply repairs.
Restart your PC afterward and see if the error disappears.
Step 8: Perform a Clean Boot to Identify Conflicts
Sometimes, third-party software conflicts lead to ERROR_91.
How to perform a clean boot:
- Press
Windows + R, typemsconfig, and press Enter. - In the Services tab, check Hide all Microsoft services.
- Click Disable all.
- Go to the Startup tab and open Task Manager.
- Disable all startup items.
- Restart your PC.
Test the application again — if the error doesn’t appear, re-enable services one at a time to find the culprit.
Step 9: Restore Your System (If Needed)
If ERROR_91 started recently, you can revert Windows to a previous state before the issue began:
- Press
Windows + R, typerstrui, and press Enter. - Choose a restore point dated before the error started.
- Follow prompts to restore your system.
This won’t affect personal files but may uninstall recent apps or updates.
Bonus Tips: How to Prevent ERROR_91 in the Future
- Regularly update Windows and your software.
- Use trusted antivirus software and run routine scans.
- Avoid editing application code or macros unless you understand the changes.
- Back up important data and system restore points regularly.
- Document your troubleshooting steps to ease future fixes.
Final Words
ERROR_91 can be frustrating, but with a little patience and methodical troubleshooting, you can get your Windows system or application back to normal. Remember to work step-by-step, keep your PC updated, and don’t hesitate to seek professional help if necessary.
Did this guide help you fix ERROR_91? Share your experience or ask questions below — we’re here to help you every step of the way!
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