Wireless drops if not right by router

Hi everyone,

I have a Macbook 13 inch that was bought in August 08. My screen went out and had it repaired (not by an Apple Store as was not able to be near one until recently). Once I got it back my wireless started dropping if I'm not within 5 feet of my Linksys WRT54G router. Thinking that the repair person messed something up, I took it to an Apple store. They checked it over, didn't find any problems and just reseated the wireless card but it still did not fix the issue. I was running 10.5.8 but updated to 10.6.8 but still no fix. Any suggestions or does my wireless card just need to be replaced?

Also on a side note when running Netflix Instant, my computer kicks on the fan instantly and activity monitor shows that Firefox is running an extreme amount of my CPU, any suggestions on that also? Thanks in advance!