hello world runs with fatal error

I've installed Miktex 2.9 on a win7 using all defaults. When I try to
compile the simple

\begin{document}

Hello

\end{document}


i receive the following error:

! LaTeX Error: The font size command \normalsize is not defined:

there is probably something wrong with the class file.


i assume this is a common error because i've used a fresh miktex installer
with defaults on a relatively new win7 machine and tried to run the
simplest program i could think of. unfortunately, i have been unable to
find anything related to this problem in the mailing list.

thanks for any help,
cliff
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