Well the mosquitoes must be breeding somewhere nearby in standing water, don't they?
Do you guys have two PC's? If you do, are they set up on a network or two different connections?
I guess so. There's low land all around here, and if it's not that, it's the old cars, tires and other miscellaneous junk that collects water. I think they can also breed in damp leaves and grass, but I may be wrong. Where ever it is, there's alot of it!