I guess you've got the latest and greatest firmware revision?
If so, it probably wouldn't hurt to just try a different brand. You can pick up a Linksys or SMC off the FS/T forum for around $35-$40 pretty easy. In fact I got a wireless router and was going to sell my SMC wired router, but I think I'm going to get rid of the wireless setup because I'm really not going to use it and I just don't like the security issues with it. I'll probably just add a larger switch.
Linksys or SMC would be my best choice to try, altough this wireless Dlink router hasn't given me a bit of trouble either and I have a mixed Win/Linux setup of computers...