Network Outage

Does this mean I cannot log onto my computer?

Yes, in a manner of speaking. Your computer will use what is called "cached credentials" which doesn't actually validate you on the network. The down side to this method is that when resources become available again you will not have access. You will need to log off (Start\Log Off) and log back in to gain access to network resources such as network attached printers (non-local'USB') and network drives (G:, U:, etc.).