The signal level of the client and base are not directly the cause of NSTREME trouble. You need to check the dBm senistivity of the receieve section of the radio card.
For example, if a radio card requires -71db to operate at 24mbits level, then a signal of -72 will not work well and the radio cards interal rate will drop down untill it has reached a Speed level which falls into the dBm senistivity range.
Many, of the Atheros based OEM cards out there have some manufacturing problems. The CISPA LAB tested 100 CM-9 board from one manufacture and found that the stated -71db level was different on each board. Some were better then stated in their documents, however, over 70% were worse then stated in their documents.
The bottom line is this, YOU MUST UNDERSTAND RF! Knowledge of IP and no knowledge of RF means you will never get out of the MK system what you think you should.
NEVER EXPECT SOFTWARE TO MAKEUP FOR BAD HARDWARE!