It sounds like a couple things:
1) Coincidence. The drive might be dying, and you reinstalling Windows 7 is not the cause. You can determine this by booting into a LiveCD environment such as Ubuntu or OpenSUSE and running Disk Utility on the drive. You can use short or long tests to determine any failure, and check SMART error reporting to see how many sectors have been remapped, and other stats that could be alarming. Remapping sectors is perfectly normal, but if it's a lot of them (near the "max") then the drive is likely starting to fail.
2) The drive utilizes software made by Transcend (the makers of the Storejet series) to interact properly with the drive. Best seek out the model you have on Transcend's site and see if they have utilities around that.
3) Your USB drivers could be out of date, or your chipset drivers too. Best update those.
4) Windows could be putting the drive into a power saving mode. You will need to go through device manager and go into the properties of the device and disable the power saving settings it has set there. This may not be required.