Connectivity Problems with Cisco WRT610n

I've recently started to get problems with the wireless connection to my WRT610n wireless router. The mac drops the internet connection periodically - 3 or 4 times a day. I've run both iStumbler and WIFi analyser and it doesn't seem to be the wireless connection that's dropping - just the ISP. When I try to connect to a website I just get "contacting....." in the safari status bar. The only way to re-connect is to switch airport to the other WiFi band.

It happens on both 2.4GHz and 5GHz bands. There are other low-band users on the same channel so I've hard coded to a channel that isn't being used. I've deleted all the local wireless services that I don't use from the networks list. I've blown the latest firmware into the router - none of thiese has made a difference. When it occurs, running the macbook network analyitics shows wireless green and ISP red - but I can still connect using iPhone and windows PC - so the ISP hasn't dropped.

Interestingly, while trying to fix this problem I discovered another. I cannot connect wirelessly to the router's set-up page - I have to ethernet into it. This is only a problem for the Macbook; iPhone and PC can both see the router's set-up page via wireless whereas the macbook just says "contacting.....". I don't know if these two problems are related, but I know that in the past I *have* been able to connect macbook wirelessly.

I've got a macbook pro 13 inch - I bought it in about May this year.

2.7 GHz processor - Core i7

8GB memory

1333 MHz DDR3

OS 10.6.8

All software up to date - including router's firmware.

S/N 25 to 35 dB

Thanks in advance for any help.