Thanks for the very helpful information in this thread.
I had a Sansa e280v1, and used Winamp for all my local media handling and syncing with the Sansa. Any time I'd delete a file from the Sansa via Winamp, Winamp would crash - no error messages or anything, the program would just quit. It was kind of a pain, but I didn't delete files all that often so I could live with it.
SanDisk replaced my e280v1 with an e280v2 due to a defective headphone jack. With the v2, as soon as Winamp finished loading the index info from the Sansa, Winamp would quit.
Following the help given in this thread, I uninstalled Windows Media Player 11, which reverted back to my previous WMP 9. I then downloaded and installed WMP 10 from here:
Everything seems to be working fine with my Winamp 5.531 now - it doesn't crash after loading the Sansa index info, and I can delete without problem.