problem with login

i have wheezy .i downloaded soulseek last version.at first i enter wrong username and password but know i cannot put the right ones.the program starts and informs me that login fails but when i enter the right username and password soulseek crashes.i delete the program and i extract the zip file again the same problem.it looks like that the wrong username and password has been kept somewhere in the system

gdb SoulseekQt-2013-10-5-64bit
GNU gdb (GDB) 7.4.1-debian
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License GPLv3+: GNU GPL version 3 or later
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This GDB was configured as "x86_64-linux-gnu".
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...
Reading symbols from /home/kostas/SoulseekQt-2013-10-5-64bit...done.
(gdb) run
Starting program: /home/kostas/SoulseekQt-2013-10-5-64bit
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
No protocol specified
SoulseekQt-2013-10-5-64bit: cannot connect to X server :0
[Inferior 1 (process 5153) exited with code 01]
(gdb) bt
No stack.
(gdb) bt
No stack.