aspnet_compiler: error only when precompiling without "-u" option

[Pao]

Hi all,

If I compile WITH the -u option I get no error,
but

when compiling WITHOUT -u option, I get this error message:
"error ASPRUNTIME: Object reference not set to an instance of an
object."

and I can't see in which row the error is (I already tried -d and -
errorstack option but nothing to do).

In Visual Studio Developer alla goes well.

Why do this error come out only without -u option and how can I
correct it?
thanks