17" Mac Book Pro Issue

I have a 17" Mac Book Pro that has been experiencing start up issues off and on since I updated OS X to Snow Leopard and now Lion. Originally, the computer had an issue and froze during the first attempt to install Snow Leopard. From that time on, it would not get past the grey screen during a normal start up and would start perfectly in safe mode. I reinstalled Snow Leopard via safe mode through the disk and it worked. The computer worked fine for about 3 weeks in normal use. I was downloading pictures into IPhoto last week and the computer froze again and once more it won't get past the grey screen at startup, but will start up in safe mode. Any suggestions?

Sounds like a hardware problem, if it does the same on both OS's.
You could try a hardware test, just use the original install disk for that.
Post back with the results, plz

SM