Could well be the phones .... or mobile phones, or microwave ovens.
Belkin and Firmware updates don't mix, they always seem about 18 months behind.
I have a similar setup, two desktops, one laptop with same adapter, and had the same problems. I can only run an open network, if I secure it in ANY way I get the above problems. Try a different wireless channel (default is 11) and see (it did mine) if that cures it, but forget security.