out of memory for pbuffer

Hello,

i have the problem that my pbuffer get created with no errors at

wglChoosePixelFormatARB
wglCreatePbufferARB
wglGetPbufferDCARB
wglCreateContext

and

wglQueryPbufferARB returns the correct size.

but when i use the pbuffer the program crashes at the first glDrawElements.
I think the reason is that my graphics card has not enough memory (64MB) and i use a big pbuffer (2048x2048). With smaller pbuffer or on cards with 128 MB memory everything works fine.
But why gets the pbuffer created and no errors are thrown ?

ok, obviously this topic is not interesting like benchmark cheating, nevertheless perhaps someone has an advice ?

how is the correct behaviour for pbuffers and insufficient memory ? I thought the pbuffer creation should fail then, but it does not. Has anyone else tried huge pbuffer (2048x2048) with insufficient memory ? What happens ?