WNR3500 difficulties

[DrakeBakes]

I purchased a WNR3500 in early 2011 and haven't had too many complaints due to lack of needing anything more than a basic router, but recently my problems have just become huge frustrations.
I have a desktop pc and a new laptop. When trying to transfer files from either of the machines to the other, or even downloading, my speed gets capped at around 500kbp/s. I've fiddled with channels and security settings and even updated to newest firmware but still, no progress. If anything, it has cause more of a headache. Kudos to any future help.
And please bear with me, I do not have the most in-depth networking knowledge and will submit any information I can.
I know I am using 145mbps mode with WPA2-PSK [AES] security.