align in tabular

hello,

i am trying to typeset a math align environment inside a tabular but the use of the ampersands seems to clash. does anyone know how to do this?

for example, this works:

\begin{tabular}{|p{0.9\textwidth}|}
  foo \\
  \begin{equation}
  x = y
  \end{equation} 
\end{tabular}

but this breaks latex:

\begin{tabular}{|p{0.9\textwidth}|}
  foo \\
  \begin{align}
  x &= y \\
  a &= b
  \end{align} 
\end{tabular}

cheers,
andrew.

-- 
Andrew B. Collier

Antarctic Research Fellow                         tel: +27 31 2601157
Space Physics Research Institute                  fax: +27 31 2616550
University of KwaZulu-Natal, Durban, 4041, South Africa