Yes, btcguild is a separate bug, sorry. BTCguild is the only pool that uses the redirect feature in stratum which was added blindly a long time ago when stratum support was first added and no pool used it. Cgminer's implementation is unfortunately buggy and the only workaround till I can fix it is to connect directly to btcguild's redirected url directly or use a different pool to avoid the crash.
I can confirm this bug, but for me this appears seldom.
I also have problems with another pool:
http://elizium.name/ (p2pool). After minutes I get: ./cgminer: double free or corruption (!prev): 0x0a01f120 *** with backtrace.