Just a shot in the dark, but you might want to make sure you're not writing a byte at a time.
Check your debugger cfg file and make sure you see 4's for dword access,something like this:
range 0x00000000 0x0001FFFF 4 Read
reserved 0x00020000 0x1FFFFFFF
range 0x20000000 0x20003FFF 4 ReadWrite
reserved 0x20008000 0x3FFFFFFF
reserved $IPSBAR_BASE + 0x200000 0xFFFFFFFF