Huge slowdown of system after cleaning & repaste?

Some of you might know me, and no, im not a Toshiba owner, but i have a friend whom i helped clean his laptop - a Toshiba Qosmio F30, which was overheating due to dust buildup and tim degradation (after 3 years of heavy use).
We followed the Maintenance manual to dissasemble the laptop, clean the heatsinks and fans, repaste it and put it back together (tripple checked every cable is where it belongs and every screw is in its place).
After we turned it back on, the laptop worked, all hardware was detected normally, it now runs cool as it should, BUT the system got painfully slow... CPU usage in windows (Vista) shows 100% CPU use at idle, it even struggles with safe mode...
I have absolutely no idea what this could be... Ive taken apart, repasted, cleaned and upgraded a decent number of laptops so far (even did some previously untested mods), but ive never encountered such a problem - if something was out of place it didnt work and i could fix it, here i cant find anything i could have done wrong...
If anyone has any idea do share em .

 

I took it completely apart again today, checked my repaste (and did a fresh repaste again) and put it back together, and now it works better than ever... I have absolutely no idea what was wrong becouse nothing seamed out of order when i was taking it apart and checking it, but it no longer matters. Just one of those days i guess...

 

That's good news, congrats for going back and doing it over. Must have been frustrating.

 

I'm glad you fixed the problem. You think repaste was the problem or maybe some weak connections?