What OS are you using? What model of Linksys router? Have you recently updated the firmware for the router/have you update it to the latest release in the past?
You could try reinstalling your wireless adapter's drivers from the manufacturer's website.
I would try to reinstall the wifi adapter driver first, then login to the router and make sure you have the latest firmware.
Theres really many variables that could be effecting your connectivity at this point, and I've seen various issues ending up being the root cause, from IP conflicts to bad WiFi Adapter cards, to router firmware malfunctioning.
