A few Mediacom customers have had connection problems lately. I can't find any evidence that Mediacom are currently 'blocking' p2p somehow, but that doesn't necessarily mean that they're not. If you use Google to search for Mediacom blocking p2p, there are quite a few articles but they're all really old.

In LW go tools > options > advanced > firewall config & check the 'manual port forward' radio button. Enter LW's listening port number into the box there. Even though you don't have port forwarding set up for a modem/router...try it anyway!

Do you know whether anybody else in the apartment complex uses p2p successfully? Is Mediacom the ISP for the whole complex or did you choose your own ISP?

Try one of these other p2p apps & see whether you can connect with any of them.
FrostWire

Phex

BearShare