Getting stuck on Welcome Screen

I have the following basic system setup :

Precision T7500 (Xeon 3.4GHz + 12GB ECC Memory, 2.5GB Quattro Graphics, Internal Wireless/LAN adaptor(

I have the following items plugged into it :
2 x Drobo Backup Robots (at 8TB each) plugged into rear.
1 x Powered USB hub which has :
  2 x Apple charging cables (not in use)
  1 x Logitech C910 HD Webcam
  1 x eeePad Transformer charging cable
  1 x Unifying Receiver (Logitech)
  1 x Charging cable (for Logitech Mice/Keyboard)
1 x Bluetooth receiver

The system is running Windows 7 and I have the following software :
  Acronis True Image (using the second Drobo)
  Trend Micro Maximum Security 2012
  Adobe Web Developer CS 5.5

Today I cannot get the computer to boot through to the actual desktop with it only getting through to the "Welcome" screen.  I attempted to restart the computer and I get the same issue (after logging in).  It also does this in Start Mode.  So I pulled everything out and it started fine (actually it started much quicker than it usually does).

During one attempt I got into the desktop but ended up with the following error :
OK_c_pers.exe has stopped working.......

I've done a bit of a search on this but no one seems to know what it is.
Windows Explorer then stopped running and I had to reboot again.

I'm wondering if one of the Drobo's is causing an issue?