This is what i get:
warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148)/Symbols/usr/lib/info/dns.so (file not found).
2011-02-26 21:17:43.274 Treacle[2493:5c03] [NMSP_ERROR] readCallBack(): Network error, calling closeCallback! Error:2517952
2011-02-26 21:17:43.284 Treacle[2493:5c03] [NMSP_ERROR] writeCallBack() Received error kCFStreamEventErrorOccurred.
2011-02-26 21:17:43.539 Treacle[2493:307] [NMSP_ERROR] check status Error: -12986 -> line: 434
2011-02-26 21:17:43.689 Treacle[2493:307] [NMSP_ERROR] check status Error: -12986 -> line: 434
I don't know what file it has a problem with at line 434 but on my view controller.m that line has been there for ages without causing problems and is contained in a method, which isn't triggered when the app starts.
This is a known problem. Just go to /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.2.1 (8C148) and copy /Symbols/usr/lib/info/dns.so file from 4.2 Symbols folder to 4.2.1 (8C148)/Symbols/usr/lib/info folder. It's just not there. Quit your Xcode and open it again. It should work.