I'm not sure what happened, but it happened twice: While doing a multi-file diff, I was examining the differences between two files and towards the end there was a large section (100+ lines) where it just showed all inserted lines + deleted lines as the difference -- the 2nd file had been corrupted so it was mostly just empty lines while the 1st file had what was expected. Both files were open in SlickEdit before doing the diff. I closed the diff, and switched to the 2nd file, and it appeared the same as it was in the diff -- mostly empty lines at the end. I closed the file and reloaded from disk and the file was OK. I repeated the multi-file diff, selected this file pair again, and again saw the same corruption. Closed the diff and reloaded the file from disk and then did a single file diff of the same pair of files. Everything looked OK with that. I proceeded to move some of the diffs from the 2nd file to the 1st file. Now, if I do the multi-file diff, the problem doesn't re-occur.
I'm running with Windows x64 beta 2 on Windows 7. File 1 (all the files in path 1) was R/W. File 2 (and all the files in path 2) were R/O on disk. All files were being accessed through a Samba network share (on AIX server).