well, you're surely not giving us all the information, because if i
typeset what you've provided here, i'll get a list of two items marked
by A and B.
but try resetting the list manually if you don't want to give a
minimal working example:
\begin{enumerate}[A]
\setcounter{enumi}{0}
\item Item One
\item Item Two
\end{enumerate}
cheers,
jon.