Regarding Database Display through user interface

Hi ! I'm writing a small app/Acquisition System.I coded for that and while compile time iam not getting error.
At run time getting like this:

Unhandled exception at 0x650b02a6 (QtGuid4.dll) in Acquisition.exe: 0xC0000005: Access violation reading location 0xccc35df1.


I attched my code.Please tell me how to solve the Access voilation Error.


Advance thanks for all.
Tavit.

Please provide a backtrace from the debugger.