Lotus 123 files become corrputed off network drive

We have recently upgraded our network to Vista and server 2008. Some of our users lotus 123 Lotus v9.8 files (I know we still use Lotus 123) which are on the network drives are becoming corrputed after they save the file. Everything works correctly when editing and saving but when they try to re-open, the file is corrupted. We have had the file even go to a zero byte (meaing the file size went to 0 bytes). This will happen randomly and I cannot figure this out at all. Sad part to all of this is that Lotus 123 will not tell you there is an issue with the file if you just hit the save button, but when a user hits the save as - the error that the file has become corrupted shows up. I know I should tell the users to just convert to Excel - however we have a spreadsheet with like 25 tabs that does not work well with Excel... this is one of our main sheets that are used on a daily basis.

I thought it was a network problem because Lotus does not like it when you disconnect from the network while a file is open, but we have had users switch PC's and the same issues occur. Oddly - I have run tests on the same file and left it opened (test file) for a few days and no issues occur. The sheet is shared however, the file will tell you that it is in use and is read only so I dont think that is the issue, but I am not ruling it out. This all worked fine off an old 2003 server with Vista, XP and 2000 client machines.

Any help on the issue on trying to solve why would be greatly apprecaited.