Strange behaviour wired network in combination with Wireless Access Point

A challenge for the experts.....

I have a wired network in my home. All wires are connected through a
router/switch. Some of the wiring is connected directly (my pc's
downstairs) and some of the wiring is connected through outlets (a
wire goed from the router to the outlet downstairs to the outlet
upstairs).
Whenever I connect a PC to one of the outlets upstairs through a wire,
everything works fine....

I recently purchased a notebook with a 80211.g wireless NIC (54g) and
a Linksys WAP54G accesspoint. When I connect the WAP directly to the
router (just one cable, not using any wall-outlets), everything works
fine. However, the WAP has to be placed downstairs to do so and the
wireless reception upstairs is not optimal.
Therefore I want to place the WAP upstairs and connect it to one of my
wall-outlets. Whenever I do so however, I can't get connected to the
network (the wireless connection between notbeook and WAP is
available, but the WAP is not connected to the rest of the network).

When I have the WAP connected downstairs, the LINK/ACT Led of the WAP
is mostly on. When I connect the WAP to one of my outlets upstairs,
this LED is flashing constantly.

I do not think the problem is with the wiring of my network, since
when I connect the notebook through a cable to the outlets upstairs,
everything works fine.

Does anybody have any idea what's going on and what can be done to
solve it ?

Any help would be greatly appreciated. Please respond in this
newsgroup aswell as by email to moesasji@-SPAM-bonbon.net (remove
"-SPAM-" before mailing).

Moe