I have two Apacer HA202 flashdrives, 1Gb and 2GB. Neither has given any trouble until now.
This morning I plugged the 1GB into the computer and got the usual musical tone, but no screen appeared. It didn't appear in the bar at the bottom where opened programs or devices appear either. This freaked me out more than slightly, because I keep important work on this device. Fortunately it's all duplicated elsewhere, but I now have what seems to be a phantom flash drive.
Yesterday morning I loaded some files from the desktop on it - they were startup or setup files mostly, with a few freezip files as well. They were all on my desktop and have been sitting there quite happily. Could they be the problem?

Does the other drive work if you plug it into the same port where this one does not? Just to verify that the port is OK.

Does the one not working work on any other computers?

What kind of startup files did you load on it?

You might also try re-booting with the drive installed.

There are four USB ports along the front panel. The 1GB doesn't produce a display in any of them, but the 2GB is fine in all of them.
I went to the Troubleshooting section and uninstalled then reinstalled the driver. No change.
Had this much of an idea anyway: I've just opened My Documents and hit search with the 1 plugged in, and clicked on Folders. The 1 is there in the tree under My Computer and everything shows.
I've just deleted the programs and setups that I placed there yesterday, and guess what! Back to normal. Why should these items have caused the problem though?
This pretty much sums up my feelings.
http://www.pritchettcartoons.com/comp-dog.htm

What exactly did you place there yesterday?

.....always worth a second post. I was wondering what if that was a seeing eye cat?

MyFonts Order M712675 - Windows Installer Package

spacecadet - freezip zip file
mdraw - freezip zip file
VirtualDub-1.6.17 - freezip zip file

DVDRegionFreeLite59 - Application
gdsol - application
GoogleVideoPlayerSetup - application
divx5 - application
SkypeSetup - application
nentenst - application
RCSetup - application
BIPCPSetup - application
BIRemove - application
(Black Ice) update - application

Ah yes, that mouse!

Some mice can save your life!