The problem is whether the dropped signal is due to the wireless
adapter or the router itself and as Leslie Anne says you may end up
replacing one or both. FWIW I've had trouble with connectivity on
Buffalo routers and they do appear to be more susceptible to dropped
connections due to interference, Mobile phone / DECT phones being the
major culprit here so make sure these are not near the router or
line-of-sight to the adapter. Also worth mentioning that with Wi-Fi a
small change in the location of either router or adapter can have a
large effect on the quality of connection so try this too.

Question: When the connection drops what happens if you unplug the USB
adapter and plug it back in again ? If it restores connection for a
short time then I'd suspect the adapter rather than anything else so
try a different one.