DLL Imported function gives error at first time

I had window based project in VS2005 .net framework 2.0. In that i imported some third party c++ dll's to implement functionality. It works fine here.

Currently i upgraded my project to VS2012 .net framework 4.5.

Problem is when i run my project first time, when the call hits to Dll imported function it gives exception,and due to imported function i am not able to catch this exception.

(Call hits to DLL imported function at some Winform show call)

But when i closed oped that same form again the dll import function works fine onwords.

What happend at first time my project run and call hit at first time to function?

Please give me the solution.


Suraj