Pinned memory error

Hello, please tell me why is not working Example 2. Example 1 is working fine.

Those. If I allocate a large chunk of memory before cuMemAllocHost. That all works.
Otherwise, an error on cuMemsetD32. Why?

win7 x64 istalled

Example1:

pinnedmem.i
*a=allocatememory(1600000000)
cuMemAllocHost 	(@pinnedmem,256)

cuMemsetD32 	(pinnedmem,0,1)

Example2:

pinnedmem.i
cuMemAllocHost 	(@pinnedmem,256)

cuMemsetD32 	(pinnedmem,0,1)