I have the exact same problem. I can log into the camera from 2 different PCs and one it works fine - files are there and can be manipulated from file explorer, and the other PC I get the situation described here. Both are windows 7, just different versions.
The interesting thing is that when you see the files via the "start recording" function (save as), you can actually select them, select properties and even Open them with Quicktime, Windows Media Player and even with Media Center - which lets you burn it to DVD as a file or movie without problem. If you try to copy/paste file from this window to somewhere else, it says file can't be found. Same with several other function, like adding to a zip file. Really odd.