placement new + array +alignment

SomeObj<unsigned int>* Buffer;
char* BufferPtr = MemoryManager::giveMeSomeBytes(resX*resY*sizeof(SomeObj<unsigned int>));
Buffer = new(BufferPtr) SomeObj<unsigned int>[resX*resY];

when I step past these lines with the debugger, it shows me the values for the variables Buffer and BufferPtr:

BufferPtr: 0x0d7f004c
Buffer:    0x0d7f0050

I don't really understand why those values differ. The way I understand it, placement new should use the memory starting at address 'BufferPtr' to initialize the array elements using theyr default constructors on the allocated memory and return a pointer to the first byte of the first element in the array, which should be exactly the same byte as passed to the placement new operator.

Did I understand something wrong or can someone tell me why the values differ?

thanks!

//edit: ok - i investigated the issue further and got more confusing results:

    int size = sizeof(matth_ptr<int>);

    char* testPtr1 = (char*)malloc(a_resX*a_resY*sizeof(int));
    int* test1 = new(testPtr1) int[a_resX*a_resY];

    char* testPtr2 = mmgr::requestMemory(a_resX*a_resY*sizeof(int));
    int* test2 = new(testPtr2) int[a_resX*a_resY];

    char* testPtr3 = (char*)malloc(a_resX*a_resY*sizeof(matth_ptr<int>));
    matth_ptr<int>* test3 = new(testPtr3)matth_ptr<int>[a_resX*a_resY];

    char* testPtr4 = mmgr::requestMemory(a_resX*a_resY*sizeof(matth_ptr<int>));
    matth_ptr<int>* test4 = new(testPtr4)matth_ptr<int>[a_resX*a_resY];

the debugger returns me the following values for my variables:

size: 4

testPtr1:0x05100418
test1:   0x05100418
testPtr2:0x0da80050
test2:   0x0da80050

testPtr3:0x05101458
test3:   0x0510145c
testPtr4:0x0da81050
test4:   0x0da81054

so it clearly must have something to do with my generic smartpointer class matth_ptr so he