Weird wireless channel problem

Hi, i have been using 802.11b for about 6 months everything work fine (although i need to keep changing the frequency every month because of interference). Recently very weird problem happens to my neighbourhood. I scan using snooper tools on mikrotik to find the usage of each channel on my environment, i found out that channel 2-8 has no AP on it. So i decided to change my AP (omni antenna) using any those channel, but the result is my client couldn’t associate with my AP, no matter how many times i restarted the AP or the client, the results is the same. THe distance between my client and AP is 1 km (LOS). Does anyone know what is the cause of this weird problem? Please some wireless guru help me with this. Because channel besides 2-8 is very crowded in my area, so i am thinking of switching to those channel.

I have got another question, does 802.11a would be really free from interference? I wish to try this but i need to suggestion about it first. Thank you everyone.

What kind of client hardware are you using? The clients should be following the AP when changing channels.

The only way to know if 5.8 in your area has any clear channels is to do a sight survey with a Spectrum Analyzer. You can find places on the internet that will rent one for a reasonable price. Electrocomm comes to mind if your in the US.

Dan