Slow Wireless Speeds (Both WAN and LAN) on Buffalo WHR-HP-G5

I have a Buffalo WHR-HP-G54 with "DD-WRT v24 RC-5 (11/22/07) vpn" firmware...

I have two wireless PC's on my network and one wired.. My wired PC gets 10MB down and 1MB up via the Internet..

My two wired PC's get on average 3MB down and 1MB up (sometimes 5mb down, sometimes 1mb down)..

I tested file transfer speed via FTP for them and it got 1.9MB via the LAN!!

Both Wireless PC's show "excellent" for the connection strength..

I tried upgrading to "DD-WRT v24-SP2 (07/22/09) std" and that didn't fix it either..

I figured I would give Tomato I try to see if that fixes it.. I just downloaded the Tomato
firmware and it says if you're running DD-WRT you can upgrade from the
web UI.. I select the tomato.trx file but the UI says "Incorrect image
file." when I try to update...

Don't know what to try now..

 Any ideas would be greatly appreciated.

Thanks