VirtualAlloc fails on specific memory address

@MarkusO:
Quote from MSDN:

The function fails if you attempt to commit a page that has not been reserved. The resulting error code is ERROR_INVALID_ADDRESS.

@Snatch:
I could allocate any memory region I tried. The mistake here was that MarkusO tried to commit a page which was not reserved. I never heard about that "process address space" rule, like you call it, before.

MEM_RESERVE The function reserves a range of the process's virtual address space without allocating any actual physical storage in memory or in the paging file on disk. Other memory allocation functions, such as malloc and LocalAlloc, cannot use a reserved range of memory until it is released. You can commit reserved memory pages in subsequent calls to the VirtualAllocEx function.

seems we have to do 2 virtualalloc's
one with reserve one with commit at least i understand it that way