wireless bridge disconnections

I have the following problem:

I configured DLink DI-624 as an AP/switch (uplink port not used), and then use a DLink DWL-G810 wireless bridge to like between that AP to the Desktop. I am having disconnections like once a week (I just check it once a week, so I am not sure if it disconnects more frequent than that) [by disconnections I mean the connections still looks fine from the comp, but internet and/or workgroup computers are no longer available, and ping returns time out (instead of unreachable)] and I don't seem to be able to reconnect it without unplugging the power from both the wireless bridge and the AP. Is it normal or is there any way I can fix it?

More settings:
the desktop and router has (manually configured) IP addresses
DHCP is done by a wired router (wired router's LAN connected to AP's LAN ports) and disabled on the AP

WPA-PSK is on, tried both SSID enabled/disabled, and the connections runs fine when I replug the powers for both the AP and the wireless bridge.

the comp is on 24/7 (so can't turn off to install a wireless card yet)