Could even be your neighbours using their wireless on the same or 'neighboring' channels, there are only really 3 wireless channels, with a slight variance between each giving the additional channels you see, the main ones are 1, 6 and 11 with two 'neighbors' either side bar channel 1 which doesn't go into 0 or -1 as it's at the start of the wireless frequencies, if that makes it easier to understand.
Is there a specific time it goes tits or is it random?
If you really wanted, you could monitor things with
http://www.netstumbler.com/ whist it's up and working make some notes of the networks you see and channels leave it running for a while and save all the info, and when it goes wrong makes some notes about the wireless network names and channels they're on etc and comparing your notes to figure out which has the least neighbours when it's going tits. but tbh, the home plugs and a network cable to the laptop and/or a wireless cable router should add enough extra network ports (good for network printers, NAS drive etc ) and wireless access for you and cheap enough to set it all up coming in at around £30~ all in for the Home Plugs and a cheap Wireless Cable router, or £15~ for cheap Home plugs and a network cable