Sandisk cruzer 32GB appears and disappears from Computer

USB Flash Drives All other USB Flash Drives
4

Some of these devices have life time warrantees, not all, check with the RMA before throwing it away. 

http://kb.sandisk.com/app/answers/detail/a_id/5232/ 

Also check this thread:

http://forums.sandisk.com/t5/All-SanDisk-USB-Flash-Drives/Windows-7-Explorer-not-showing-drive-while-it-shows-in-computer/td-p/285020

You may have a conflicting app running.