Hmm. At min.. getting a 3rd party router.. even a cheaper one... and putting the unit into bridge mode.. SHOULD fix most wireless issues, especially if you are even right near the modem.
It does sound like to me, that something is amiss.
Does the same dropouts or anything happen, if you are WIRED into it?
(just trying to eliminate an issue of the MODEM droping... so signal dropout, etc)
Otherwise, i would have to agree with Datalink.. that its likely a wireless interfearance issue.