Cannot access memory at address 0x4

Hi All ,
In my Cocoa Application I am trying to transfer files between different terminals .Well likewise everything works fine, the transfer starts and then suddenly it halts displaying the following RunLog :

#0 0xffff07fc in objc msgSendrtp


[Session started at 2007-08-14 17:25:51 -0700.]
GNU gdb 6.3.50-20050815 (Apple version gdb-573) (Fri Oct 20 15:50:43 GMT 2006)
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This GDB was configured as "i386-apple-darwin".
Loading program into debugger…

Program loaded.
sharedlibrary apply-load-rules all
Attaching to program: `/Users/gada/TestingRBUDP/RBUDP 6_26/build/Debug/RBUDP_6_26.app/Contents/MacOS/RBUDP_626', process 3141.
Unable to restore previously selected frame:
Unable to restore previously selected frame:
Unable to restore previously selected frame:
Cannot access memory at address 0x4
Cannot access memory at address 0x4

Unable to disassemble objc msgSendrtp.
(gdb)

I would be very thankful if you can give me some suggestions .