422487 Vulnerability

i have application that run in windows 2003 and it open port 1995 the application run fine but the attackers do some thing i am not sure what to cause the application to give the fallowing error Microsoft Visual C++ Runtime Library Buffer overrun detected Program: C:\xserv\bin\[login to view URL] A buffer overrun has been detected which has corrupted the program's internal state. The program cannot safely continue execution and must now be terminated. *this problem happened with me a year ago the attackers use to request some thing like this and when he do my application give the buffer overrun error http://ip:1995AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/xxxx\xxxxxx// and a year ago since i don't have the source code for the application a programmer give me a dll file i put beside the software before i run it to protect the software the application called [login to view URL] and when i run the software with the dll beside it it create [login to view URL] file have 2 lines bind+ 51975 and the dll actually fixed the bug i need some one to find out what cause the problem to happen and find solution can any one help me with that