LaTeX tabu package breaks Vim spell and syntax highlighting

Question

The first line of this section of LaTeX code breaks syntax highlighting and spell check whenever I scroll to the area of the document that contains it:

\begin{tabu} {*3{X[l$]}}
    col1    & col2  & col3
\end{tabu}

This is what it looks like:

As you can tell I'm using the (excellent) packet tabu, and it's when I apply the column descriptor multiplier that things goes astray. It does not happen until I get that part of the document into the view port, so if I start at the end of the file it is fine until I get to that line (182 in my example image). The moment that line goes into view, everything bellow it is bogus.

It looks like there is some problem with the curly braces, which are marked... But I have no idea where to get from here.

Cheers.