Wireless Router Problem

[MartJ]

I have a Linksys WRT54GS router, which until now has given me no real issues, that is until we set the spare bedroom at the back of the house up as an office for my wife's new business. The signal she gets on her laptop is low, doing some checks over the weekend, I found that there is no issue with signal in the front bedroom or dining room or outside on the patio, only the back bedroom, he conclusion I have come to is that the Microwave is between the router and back bedroom and according to the manual transmits on the same wavelength as the router. As the router has given me also 4 years of good service I was wondering if I replaced it with a Wireless N router with dual band, whether this would overcome the problem.

The microwave cannot be moved as it is built in, to move the router would cost more money than a new router.

Any views please before I go out and spend money on a new router.