What can I do to improve my wireless connection?

I have wireless internet set up in my apartment, unfortunately, the apt is built like a bunker is not exactly great for wireless signals. I have problems with the signal dropping off to nothing for a few seconds and then re-appearing. I am using the Cisco Systems WRT54-G Wireless router. I've also installed High Gain Antennas to try to negate the concrete and steel walls that the signal has to plow through. Is there any way I could solidify the link or connection, short of installing cable? This is very frustrating when i am video conferencing, or playing war-rock or 360 to just have the link terminate for no explicable reason. Any input would be great.
I have contacted tech support and those schmucks didn't tell me anything I didn't already know or try, I know there are some tech saavy people out there, help me out before I take a hammer to the router.