Have you checked windows logs to see what errors it might be tossing?
Right click Start button, click on Event Viewer, then go to Windows Logs, and Application (usually). Look at the ones that are Red with a white X. You may have to clear the log and recreate the error to see it if you have a lot of issues listed.
It's also possible that the error won't show up there either. But it's a start.
Also, did you search for the error in google?
But considering that the error says: "Unrecognized database format 'C:\....\epsolar.mdb'", this leads me to believe the database became corrupt. Only 2 fixes here would be to delete the database and let EPEver recreate it (if it will), or uninstall and reinstall the software.
Another option, if you have the software, is to open the database in MS Access and see if it can repair it. It might not be able to, though.
Btw, it's "not" a problem with .net framework. That's just the function that reported the error