SanDisk 32GB Ultra Backup USB Flash Drive became very slow / hanging. Now not working at all.

it could really only be one of two things. the hardware is getting ready to fail or there is some corruption or somthing giving the software a hard time. i would format the drive, this will erase all the data so make sure you ahve all the data stored on your computer, reload the backup application and create a new backup. if you have similar issues it is likely a hardware issue.