Currently I am on the latest version (i think) 3.10.1. I always update to the latest version when it comes out since I have not been bit by new versions for a while.
I see the word "Git" in your file path to that testcase xml file so that leads me to believe you might be using the Git feature of ReadyAPI maybe? I work on files that are under the control of Git but I don't use the Git feature built into ReadyAPI. Opening and Saving files are a pretty standard feature of ReadyAPI, so if there were more issues with that version of ReadyAPI, I would think there would have been more outcry with people in your same predicament. My only thought for your solution might have something to do with Git if that is part of your workflow. That path to your filename looks really long too. Windows usually can deal with that almost 200 character fully qualified file name, but there could be something fishy with that too.
Unfortunately, that log looks like ReadyAPI is working with that file just fine, so my suggestions would just be speculation. It might be a little continued trial and error research for you into what the root cause is. Regardless, that is not a common complaint for ReadyAPI use.
If you are using Git you may be interested in the Git Console that was recently added as a ReadyAPI update. This integration will let you make .git calls directly from the console after connecting to your remote repository. For more information on the Git Console please visit the link below.