hi, i have had my wonderful mac pro for about a year and a half.it is an 8 core, with 8 gig of ram. just yesterday i had a rash of crashes while online. i ran disk utility, reset permissions and thought that would do it. it did not. this morning it wont start up from any of the drives i have set up . i partitioned the main drive into 3 drives and have a usb back up drive hooked up and even put in the original os 10.6 disk i have to use its disk repair but it won't start up from there either. all the drives lead to a page with blue and grey pattern on the left side. have i lost my graphics card? please advise,