How is signal strength being measured on the client?
I have seen the same thing you report on Windows XP in the "show available wireless networks" with the reported signal strength bars showing different levels for two SSIDs from the same AP.
However, I noticed that the bars would re-adjust when the client was actively associated with the SSID. In my case, an SSID with 5 bars would suddenly reduce to 3 bars when associated. It pops back to 5 bars when not associated.
Checking the levels using netstumbler on the same laptop showed that both SSIDs were being seen by the client radio at approx the same power level, as you'd expect.
A Cognio spectrum analyzer on a separate laptop also confirmed the both SSIDs from the same AP were being seen at the same level at that location and that there was no signal interference other than the usual 802.11 activity on other channels.
-Charles
