I was in a hurry when I posted that, there's a lot more useful information we need.
1. How far away from the router is your wife's computer?
2. Is there anything metal, or walls/floors between your wife's computer and the router? Also, anything wireless could be causing interference. Wireless routers operate at 2.4 GHz, the same frequency as some items such as microwave ovens, cordless phones, and baby monitors. IIRC, don't you have a little one? Either end of the baby monitor somewhere near your router or wife's computer could be the culprit.
3. What is the model number of your modem, as well?
4. You mentioned the phones would get messed with. Are you referring to:
Landline phones (possible filter issue if you're using DSL)
Cell phones in general use
Or cell phones connected to wi-fi