Macbook Unibody Screen Problem - Horizontal coloured bars

[alskdj]

Have had this macbook for just over a week, purchased off original owner who bought in Feb this year with Applecare warranty. Upgraded ram immediately to a G.Skill 4Gb kit. 4 days ago, computer randomly froze with horizontal coloured bar. Called Apple next day, the guy there told me that sometimes this happens, and that I should only be worried if this occurs ago. 4 days later, we are at this present scenario: In the last hour or so, has crashed 3 times. Programs running in common were iTunes and Safari.
Has anyone else had the same problem? Should I be worried now?
I have taken photos each time this has occured, but how do I upload? Thanks

 

[r.j.s]

I'd call Apple again, tell them it keeps happening - send them the photos.

Or take it to your local Apple store.

 

[l.a.rossmann]

Try the original RAM and see what happens.

Run things like memtest and prime95(if there are OSX versions/alternatives for these tools) and see if it crashes.

 

[alskdj]

Have sent it to be checked by an Authorised Service Provider. If it does turn out it's an imcompatibility problem with the ram, will I get charged for the service?