Had same problem with IE 8. Saw input regarding System mechanic and updating. Not sure problem is in System Mechanic it self but when updating system mechanic, it may have picked up some new hits on the registry and known hits in the engine for system mechanic.
I use registry mechanic I was behind in the updates so I updated then before I re-ran registry mechanic I tried IE 8 again the same problem still there unable to start. I then went back to registry mechanic and ran with latest updates and had 481 hits majority dealt with kaspresky I did the clean then exited from registry mechanic.
THEN RAN IE 8, IT I WORKING.
I think problem is in registry, there is some entry in the registry that is causing IE 8 to hang when trying to access URL's (any web site). Then when getting the latest registry cleaner (what ever one you have chosen) and it is able to clean the value out of the registary then IE 8 runs.
my recomendation is to run the latest version of your registry cleaner before installing IE 8, then run the registry clean again after the install(just to be safe) and then IE 8 will be able to access URL's. It appears the 2 registry cleaners that are known to effectively clean the registary are 1) SYSTEM MECHANIC and 2) REGISTARY MECHANIC.
Good luck hope this helps