I really need some help... I am having problems with my Mac Pro. OS X 10.5.6 - 2.66GHz Dual-Core Intel Xeon. Here is my scenario.... 1st start up- start chime then nothing, no screen signal fan stops but light stays on. 2nd start up- start chime, apple logo with load clock, then flash to blue screen, then desktop image kicks in. The finder bar then appears but has chunks missing in blocks, icons are overlapped and duplicated or multi- colored horizontal lines followed by strobing. To over come this I have too start up from the install DVD, go to disk utilities, repair disk permissions. I then restart and everything is OK most of the time. I downloaded Cache out x and deleted my cache memory for the system and web but am still having the same problems. I have done a hardware test: version 3A119 and no trouble was found. I use my Mac for video editing and have an external hard drive to capture DV footage, but unplug this when trying to restart and test. I used to put my Mac to sleep and not turn it off for a few weeks at a time. During this time I would leave the external hard drive plugged in. I hope this has not effected anything. Thank you in advance for any help.