I looked on an older discussion regarding this problem (10.53 and itunes 7.xx-8) see discusssion
http://discussions.apple.com/thread.jspa?threadID=1538111&tstart=0
go to System Preferences, Network, Advanced, Proxies. Then get rid of the PAC setting by setting to manual and leaving the fields blank.
This worked for me, though I previously have never had a problem in two years of owning this Mac.
Obviously this is a known bug which appears to have re-surfaced.