500Gb USB Passport became really slow!

I unplugged my drive and used it on another machine to transfer data, when I re-plugged it back in to my notebook it was slow to get recognized, files transfer really slow now (read or write) and most the time the window says “Not Responding” when I do anything on the drive. I tried it on other machines and it does the same thing “Not Responding” for a long time before it reads or writes.

I deleted the partition and wiped the drive with DoD sanitization, re-format as NTFS and it’s still sluggish and causes the not responding issues. In another thread that I couldn’t find the reply button for (i really have no idea where it is) Mabkay says to download the DLG from   http://support.wdc.com/product/download.asp?groupid=505&sid=2&lang=en and see if the drive is ok. The program does not see the drive, it only sees my internal hard drive. 

what would cause it to be so slow?

it could be that the drive got a logical problem after it was connected to the other computer, the cable could be bad as well. Smartware will find the drive because it was made precisely for the passports that come with it, under drive settings (setup drive) you should have a diagnostic section. You could also try the firmware update.