Slow internet access on my imac

I have a imac, about a year old, and as of late I've been having really slow internet access. Pages come up slowly in Safari and Firefox. It's usually super slow when I first turn on the computer from sleep mode, and speeds up to painfully slow after a few page views.

Internet access is through a DSL connection connected to a wireless router, but my mac is hardwired to the router. I have a pc laptop which I connect wirelessly to the router and it runs just fine, so I don't think it's the router or the DSL connection. I think it's something with my Mac.

Have others seen this problem? Any fixes?