I would suggest a bit more research into how, what and possibly who is providing your internet access. Who has control of the "switch", what does the "switch" connect to? "A few buildings away"? How far is the run (100 meters is pretty much it for reliability with UTP cable) and anything along that run that could potentially cause interference (cross-talk) will also impact reliability.
Do you have the option to test your computer in another environment, or perhaps test another computer in your environment in order to help further diagnose the issue?
Has the connection ever worked to your satisfaction in the recent past and if so was everything about the hook up the same?