Wireless Network help

[Mead]

My wireless lan is not working correctly. Im using dlink 520+ nics and a dlink 614+ router. I'll boot up and it connects just fine, I'll have a really nice connection just like with my ethernet connected pc's, then it slows to a crawl and disconnects completely. I went and bought a dlink 800AP+ range extender and set it as a repeater and im haveing as much trouble as before. The signal strength usually sits between 60 and 70% up in my room, but the signal quality is between 95 and 100% always.
Ive been working on this off and on for a couple weeks now and its driving me crazy. Any ideas would be appreciated.

do you have the latest firmware installed on the wireless devices?

[meese]

Maybe its your ISP? Can you get online with a wired device when the dropout occurs?

[Mead]

Ive tried all the different firmware versions right now im using an older version because it seemed to work better than the newest one. Its not my isp, the only computers on the network that have any problems are the two connected via wireless.