A shot in the dark here but ....
I've modded my xbox v1.6 with a 2.6CE using a solderless Xapter v1.6. Things were woking fine but because Ive not completely closed up the xbox enclosure hence ... I had my xbox FRAG yesterday. My resolution were:
1. I think that the 2.6CE chip was slightly "knocked off" hence remove the HDD and DVD enclosures and resit my 2.6CE
2. After resitting the 2.6CE, the box still FRAG and I found out shortly after that by "hard pushing" the IDE connector to the HDD, the box came good again.
I do notice that once I used AutoInstaller (AI) to install the apps and did NOT use AI to shutdown the box but instead simply power the box down. This I think caused the HDD to be unlocked and hence I could not boot into either the original MS-Dash or Evox. The box would FRAG in either dash with MS giving an error message to contact MS Support. To resolve this, I booted into FlashBIOS v1.0.1 and locked my HDD.
My suggestion is:
1. Remove the enclosures (DVD & HDD), had the devices plugged in but nothing sit on top of the 2.6CE
2. If the box FRAG, unplug the connectors and replug them in - push them REALY hard
3. If still FRAG, resit the power cables to HDD and DVD drives.
3. If still FRAG, boot into FlashBIOS if you can and lock the HDD.
Good luck