This probably wont help at all, but be sure that you give the usb device at least 30 seconds before declaring it not found. I find that not all devices (especially ext hdds) will show up instantly.
I have three flash sticks. Two of them wouldn't read but the third didn't have any issues. I noticed the flash drives that didn't read, both had one of those special partitions from the manufacturer (for their own special windows backup software) while the one that worked was a plain Jane flash drive with no special partitioning.
On a similar note, both of my specially partitioned flash drives were corrupted. One of the two partitions got scrambled and I no longer have access to the data I had stored on them. Luckily they weren't storing any unrecoverable data.
On my Acer it takes about 4 minutes to mount my external portable 500 gig drive. But once its mounted its all good, currently sorting 10 years of photography on it right now with File Manager HD.