problem with indentation and emacs

[Markus Jais]

hello
I have a problem which drives me crazy!

when I cut and paste some code within a *.py file
then there seems to be problems with identation.

everything looks fine, but the programm crashes with
syntax error or with "IndentationError: expected an indented block"

when I look at the code, everything looks o.k.
when I open the file with vim and reindent everyting,
the programm works.

when I reindent it with Xemacs, I got the same errors

maybe this is a problems with tabs and spaces, but I couldn't find
out anything.

please help. Xemacs is cool and python is cool. but I want to use
them together.

markus