If this connection was working and has become unstable, then I would make sure that you are connecting to the correct router. Many people, (and this may include yourself), don't change the default name of the router network from the manufacturer's original setting.
In the case of the Linksys router, the router network would appear as "Linksys", and you may actually be connecting to a neighbor's router that is too far away to be a stable connection.
As the other two people have suggested, you may want to make sure that you are closer to the router, but really, make sure you are connecting to YOUR router. I would change the name on your router to something unique, to be sure it's yours, then connect to it, this may fix the issue.
Also, if it was working well, and now is not, it could be that the wireless portion of your router is beginning to fail, this being an indication that your router is in need of a replacement.
I hope this helps.