Slow USB Ports

I have a mid 2009 13" MBP, 320 GB hard drive about 70% full. It is connected to an external hard drive via a powered USB hub. The external drive is split into two partitions, one for Time Machine and one to clone the MBP. I use Super Duper to make the clone. The TM partition is almost full but the back-up partition which is sized to match the 320GB hard drive has room.

Historically, a first clone would take about 2 - 3 hours and then subsequent incremental (Smart Backup) clones would take 30 - 40 minutes. For the last few clones, the back-up time has increased significantly. I did one last night (Smart Back-up) and it took over 7 hours. In watching the back-up statistics, the clone starts at around 50 - 60 MBps and then drops off to 10 - 11 MBps and sometime as loww as 2- 3 MBps.

I have tried using a different external drive and even connected the drive directly to the USB port on the MBP to eliminate the hub and cables as a possible bottleneck. Using the second (other) USB port on the MBP makes no difference. I thought perhaps it was software related and tried a trial version of CCC but the results were pretty much the same.

My concern is that the USB I/O controller is failing or there is some other hardware issue developing.

Any thoughts on what might be the issue or how I can trouble shoot this further?

Thanks,

David