GPU temp probs after dis-assembly/reassembly

[Agera One]

My Sony Vaio VPCEB34En laptop's CPU and GPU share the same heat sink and fan. I removed for cleaning purpose. After I cleaned my fan, I mounted them back. At first, the laptop didn't power up and the fans are not spinning. Then I checked to see whether my CPU is seated well and it wasn't. I fixed that well and now using the laptop. But the GPU and System temps from Speedfan were showing high temps. Here are the conditions:

Before dis-assembling CPU-GPU-Fan assembly (SpeedFan temps with one-tab browsing):
CPU 46-48 C
GPU 56-58 C
System 56-58 C
CPU Fan 4260 RPM (this was the highest recorded RPM even when playing games)

After dis-assembling and reassembling CPU-GPU-Fan assembly (SpeedFan temps with one-tab browsing):
CPU 46-48 C
GPU 65-68 C (at most went to 73 C)
System 65-68 C (at most went to 73 C)
CPU Fan 4500 RPM

So where did I made the mistake that made GPU alone go hotter but not the CPU?

 

[qazzi]

please don't use speedfan. it's rubbish!! use HWmonitor here http://www.cpuid.com/softwares/hwmonitor.html

 

[jbd12345]

The thing that comes to mind is thermal paste. Did you reapply it or just leave it?
Edit: +1 for HW Monitor. Shouldn't matter that much but just to be safe...