Focusrite Scralet 6i6 issues

I recently purchased a Focusrite Scarlett 6i6 to use with my portable Pro Tools rig. Installing it was no problem, and it ran right of the box. Where I’m running into a problem is when I switch sessions at different sample rates. I have some older sessions that were created at 48k, and I want to keep them that way. Initially, I thought I would change the sample rate in the Mix Control panel and re-launch Pro Tools. As soon as I push play, I get an error message in Pro Tools saying - “Pro Tools could not initialize the Focusrite USB 2.0 Audio Driver. Please make sure that the device has been configured correctly.” The software hangs, and I have to shut it down by way of the Task Manager. I’ve looked on this forum, but I cannot find a solution. I even tried to download and install the version 3.1 driver. It wouldn’t even recognize the hardware. I consider myself to be pretty computer literate, so if anyone has a suggestion, feel free to get as technical as you like. Please see my specs below.



Computer - Model : HP p6-2123 103C_53316J G=D



Processor : Intel(R) Pentium(R) CPU G630 @ 2.70GHz (2C 2.7GHz, 2.7GHz IMC, 2x 256kB L2, 3MB L3)



Windows 7 Home Premium 64bit (Service pack1)



Total Memory : 8GB DIMM DDR3



Pro Tools M-Powered 11.3



Focusrite Scarlet 6i6



Mackie Onyx 1640i (M-Audio