Imac 2009 freezing up on startup

Question

I have an iMac 2-3 years old, an Intel 2.66mhz core 2 duo to be exact.  Lately, the computer is freezing during start up at the point where the grey dashed circle is spinning.  It literally stops spinning and just sits there.  The only thing i can do is hit the power button and restart--then it usually starts up without a problem.  I have all the latest software and updates and have run disk permissions.
What is going on??

Answer 1

I too have had this problem with the computer freezing up. I tried all the fan controls, upgraded memory, clean install of OSX and it did not solve my problem. It did help with the cooling a lot though.
  I replaced the HD with a Seagate SSHD 1TB model and it has solved the problem. I still get a little freeze if I over run the memory or max out my CPU use. But the SBBOD or Spinning Beach Ball of Death is gone. I have had very few freezes since then and that was me trying to make it freeze up.
My machine is a late 2006 iMac 24" with 2.33 GHz processor, 1 TB SSHD, 4 GB RAM but systems only uses 3 GB with the Nvideo 7600GT 256MB video card. My machine was a CTO but only had 2GB Ram and 750GB HD when I ordered it in November 2006.
Temps are as follows:
CPU   33C  max according to intel is 100C  fan is at 2700
HD     33C  max according to Seagate is 60C fan is at 3000
GPU   36C max according to Nvideo is 64C fan is shared with CPU at 2700
ODD   32C and the fan is set at 600.
I use SMCFanControl and the modified default setting. If and when I really strain the system and it get hotter I use a custom setting of:
ODD 3675
HDD 4014
CPU 2987 to 3200 max RPM.
I have removed the front face place and drilled holes to increase airflow bring more cooler air in and that helps some with the cooling. That is a big process in itsself.
Lets say the apple logo on the front is surrounded by 79 holes and then on the top 37 holes and you can feel the heat coming out the top.
Hope this helps you or anyone that is having this problem. 
Tim