Knowledge Base

Summary 

A CatWalk XT experiment would not open. When the experiment first complained that it was created in a previous or newer software version, renaming the version.dat file to version.dat.old resolved the issue. Later, when the message appeared again, the version.dat was renamed to version.dat.old2, and the experiment immediately showed an unexpected error. Renaming or deleting this second file did not help, and attempts to delete corrupt settings files also failed. Other experiments opened correctly, so whether there was a way to salvage their main experiment. There are three possible reasons why CatWalk experiment show the unexpected error. The three FAQs below explain the detail and step by step instructions on how to fix the error

FAQ 1 – How to Fix the “Unexpected Error” after renaming version.dat 

Why does the error occur after renaming version.dat? 

CatWalk XT uses the version.dat file inside each experiment folder to track the software version used to create the experiment. If multiple .old copies exist or the file is missing altogether, the software may throw an unexpected error when opening the experiment. Renaming the file incorrectly or deleting it can break the experiment. 

How do I fix the error and open the experiment? 

Follow these steps to restore the correct version.dat file and resolve the error: 

1. Locate the experiment folder 

• In Windows Explorer, navigate to the folder where your CatWalk experiment is stored (usually under C:\Users\Public\Documents\Noldus\CatWalk\Experiments or a similar path). 

1. Revert the filename 

• If you see files named version.dat.old or version.dat.old2, rename one of them back to version.dat. There must be only one version.dat file in the folder. Delete any extra .old or .old2 copies after you restore the correct file. 

1. Use a known‑good version file 

• If the original version.dat file is missing or corrupted, copy version.dat from another working CatWalk experiment created with the same software version. Paste it into your problematic experiment’s folder and rename it to version.dat if necessary. 

1. Remove corrupt settings 

• Some users fix unexpected errors by deleting settings files (e.g., Settings_*.xml or ExperimentConfig files). If your experiment still fails to open, try moving these settings files out of the folder (keep backups) and re‑open the experiment. CatWalk will recreate missing settings files. 

1. Test opening the experiment 

• Launch CatWalk XT and attempt to open the experiment. If the error persists, repeat steps 2–4 or contact support for assistance. 

By ensuring there is a single, valid version.dat file and removing corrupted settings files, you can usually recover an experiment that reports an unexpected error after renaming the version file. 

FAQ 2 – How to Replace a corrupted .cwe file 

What is a .cwe file? 

In CatWalk XT, .cwe files contain the walkway definition for each experiment. If a .cwe file becomes corrupted (for example, after a failed edit or crash), the experiment may refuse to open or show errors. 

How do I replace a corrupted .cwe file? 

1. Close CatWalk XT 

1. Go into the folder of the experiment that will not open (normally located here C://Users/Public/Public Documents/Noldus/CatWalk XT/Experiments/<your experiments own folder>). 

1. Locate the CWE file. This is the MAIN file of your experiment and it is what is preventing the experiment to open for some reason. The restore.btn file is a backup ‘COPY’ of the CWE file. 

1. Right-click on your CWE file and add ‘OLD’ to the end. For example: Spinal cord injury.cwe - change it to Spinal cord injury.cweold. 

1. Now rename the restore.btn file to what your CWE file was originally. For example: restore.btn becomes Spinal cord injury.cwe. 

1. Now try and open the experiment as before. Open CatWalk XT and go File menu/Open. Load in the experiment’s CWE file. 

FAQ 3 – Replacing a corrupted Version.dat file: Experiment will not open and error message states it was made with a previous version of CatWalk

1. Close CatWalk
2. If the original version.dat file is missing or corrupted, copy the version.dat file from another working CatWalk experiment created with the same software version. Paste it into your problematic experiment’s folder and rename it to version.dat if necessary.
3. It will ask you if you want to overwrite, click Yes.
4. Open CatWalk and try loading in your experiment again. It should load in fine now with no errors.

Please make a backup of your experiment via File menu/Make Backup. Archive the CWZ file for safe keeping. Backup daily or weekly.

These instructions address both the unexpected error caused by renaming version.dat and the procedure for replacing a corrupted .cwe file. Following these steps should help you recover the experiment and resume analysis.