It is easy to use templates, but it is hard to make them

Yes this is the template nightmare when you use it and link it to your code. Just take a look at some template libraries that we use in our everyday programming, like STL, ATL, WTL, some libraries from Boost, and you will see what I mean by this. Those libraries are great example of the principle "simple interface - complex implementation".

After hours and days finding the errors without result, I found the interesting topic here http://support.microsoft.com/kb/168958 and here http://www.unknownroad.com/rtfm/VisualStudio/warningC4251.html.

This what was happened to me. I've created a DLL from a class of mine where i use std::vector<> members to store something. My problem is that when i call a library function that insert an element on the vector, the first operation after that one on the vector (clear it, read the first element,etc) cause an error on the heap:

Expression: _CrtIsValidHeapPointer(pUserData)
HEAP[Print.exe]: Invalid Address specified to RtlValidateHeap( 28d0000, 28e3bd0 )

Gosh, it took me days to find what the cause. Trying this trying that, use this best practice that best practice closure but none worked. Very wasting time.