Lost internet access on Repeater node

This has been driving me mad for months and I am hoping someone on this forum can help me.

I have bradband modem with combined wireless hub in my office (unit is supplied by British Telecom but it it not one of there HomeHub devices, it is a rebanded gateway.2wire device). This is connected yo the DSL and provide wireless in my office. My laptop is generally in the office and associated with this AP.

However, my house is about 50M away from the office and we have very thick stone walls so the signal in the house is very weak. So nearly a year ago I installed a wireless repeater (Edimax) near the patio doors. This appears to be a goo d setup since I get a strong signal inside the house and multiple wireless devices, including our home PC, iPad, media server and multiple friends laptops, ipads and iphones are able to access the internet via the repeater.

In order to differentiate between the main AP and the repeater they each have different SSID's (Lets call them Office and Home). The only device that I have trouble with is my work laptop. This spends 90% of it's life in my office, associated with the Office AP and works just fine. At weekends and in the evenings I bring my laptop into the house and, although it can just about see the Office AP, the signal is so weak I disconnect and re-connect to the Home repeater node. Then everything works well for anything from 10-60mins before I loose connectivity to the internet. I still have access to the devices inside the WAN, such as the media server, so the wireless connection is OK. I am thinking the problem is DNS (or other lookup), since it is only external URLs that I cannot connect to. If I disconnect from the Home repeater node and then reconnect I typically get another 10mins or so before I lose the internet connection again.

The AP is configured to use DHCP and the repeater is in a 'universal repeater' mode and does not have it's own DHCP but instead gets IP addresses from the AP pool.

When I have the issue I have tried renewing the IP lease but this has not affect.

The only thing I can think off is that the main AP expects to see the laptop connected to it directly and when the same IP address shows up via the repeater the AP shuts down the traffic in an effort to protect the network from some sort of attack. The main AP has the default firewall turned on but no other access controls set.

Like I said at the top of thie posting, this has been driving me crazy for months. Generally I just connect my laptop to the main AP from inside the house and live with the slow connection, but I would really like to understand what is going on here.

TIA