Mid-2010 15" MBP selectively not connecting to wifi

I can connect to wifi everywhere but at work.

When I try to connect to wifi at work, I get a consistent message that the connection timed out. Both wifi networks there were previously functional without issue. I recently had to rescue my hard drive and had the Apple Store install a new drive with a fresh install of Mountain Lion. Things were fine for about a week after that, and then my wifi stopped working at work.

I can get internet access via LAN at work without issue. I first thought that perhaps my MBP was being ignored by the proxy bypass set up for my MBP, but with the LAN, my access to the web is the same as it ever was. It simply won't connect to either the public or staff wifi anymore.

I have tried deleting the old wi-fi networks and creating those networks manually from scratch, to no avail.

Anyone else have issues with their MBP running perfectly fine just about everywhere except for one frustrating spot?

Solutions? Ideas?