Not long ago a spat of AUTORUN VIRUS caused Microsoft to disable autorun on memory sticks and more.
Your story tells me that your Vista may be out of date and that stick may have carried a virus. Here's 2 links about the pest and Grif with some software to scan the machine with.
http://forums.cnet.com/7723-19703_102-567309/san-disk-memory-stick-auto-run-inf-flagged-as-virus/
Grif has a fine set of scans that we use around here at this link.
http://forums.cnet.com/7726-6132_102-5098912.html?tag=posts;msg5099421
Bob
Hello,
for the first time, I attempted to transfer photos to a memory stick, but didn't get far.
When I insert the stick, a window appears telling me that the Folder is empty.
I then clicked on 'my computer', chose the 'H' drive and there the message is "please insert a disk into the memo stick drive".
Well, it's in there - how else could my PC tell me that the folder is empty?
What should I be doing? Hope someone can help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic