Wi Fi randomly works/doesnt work, Apps freeze..

I'm stumped. Im having an issue on two fronts that seem to be connected somehow. Im using a summer 2011 imac i5 8gb ram running lion. First is with connecting to a public wi-fi hotspot. I live in an apartment complex with free wi-fi (the kind where you are directed to a webpage and must agree to terms of service before getting connected.)

I seem to be able to connect to wi fi only at random times. Other times it will work flawlessly. This is an issue only on this imac, I have an iphone, windows pc running windows 7 and a ps3 that have no issues connecting to wi fi. The problem that also seems to be connected is that Apple apps freeze upon opening. It seems only to be apple made apps - Safari, Itunes, Mail and for some reason the Key Chain Access utility. Third party apps seem to work fine. I think its important to note that this issue didn't start right away but 2 months after I started to use this wi-fi hotspot.

I have tried everything from time capsule resets, deleting plist, repairing disc permissions, even wiping the hard drive and installing Lion from scratch. Nothing seems to work. Please help!

You don't say if you're up-to-date with Lion, but there has recently been a wifi update patch for iMac's 2009 onwards running Lion.
Worth making sure you're all update first before doing anything else.

Yeah I'm updated.

I'm really trying to avoid dragging this thing to the Apple store.

Boot the iMac to the recovery partition by either holding down the option key and selecting Recovery or by pressing command+r to startup. Once in Recovery, select Disk Utilities. Then click on repair permissions. Let's see if that helps with the Apple applications.

As for the WiFi problem, does the public WiFi use any form of encryption or are you broadcasting and receiving in the clear? The reason I ask is because I know from experience general public WiFi whether it's local community or apartment complex building generated, is not very good nor is it safe.