Do you see the files in your 20Data directory? If not, do you see 2 files with the same name, ending in .cache? If not, do you see two files named something like ~10234234.tmp?

For reasons I don't understand, when you save it actually creates a copy of your file with your changes as a tmp file. Then it deletes the original, then it renames the tmp file to the name of the original.  We think that in some cases that last step fails, possibly because of anti-virus or backup. However.. anecdotally it sounds like when it happens it happens during EF Acknowledgement on the file. So we're not sure.. and we are going to keep digging in til we figure out. If you can provide any clues, like confirming if they disappeared during EF Ack or at some other point.

Also, in ProSeries can you choose Help -> Send Logs and email the resulting .zip file (saved to your desktop) to proseries_engineering@intuit.com? Note that on some machines even that is failing due to permissions issues. If that happens email us anyway and we'll provide further steps.