Network upgrade

I am thinking about upgrading my network. I am currently using 2 linksys wrt54g version2 as routers one is repeating the signal using wwdrt firmware. The computer furthest away from the modem drops the signal from time to time. Does anyone have any suggestions on what routers/ modem I should get or do you think it is a computer issue.

Any help is greatly appreciated.

I would be looking at two things first:

signal strengths at repeater and bridge

interference

if I was a betting man I would bet on interference.