[XeTeX] xunicode's textipa command

[Andy Lin]

I'm currently using linguex to typeset examples, and I've noticed that
\textipa is broken within the \ex. command/environment. Upon further
investigation, it seems that even \newcommand\ipa[1]{\textipa{#1}}
breaks \textipa (although \let\ipa\textipa, as mentioned in the tipa
manual, is fine). I'm not sure what the problem is exactly, if it has
to do with xunicode setting capital letters as active in its textipa
implementation or something else, but I did find an earlier discussion
on the subject http://groups.google.com/group/comp.text.tex/browse_thread/thread/64916c5485349818/f8fdde95b0a636ba?#f8fdde95b0a636ba
though the solution proposed there was to simply input the unicode
equivalents of the IPA characters (which would break compatibility
with non-unicode LaTeX), or to come up with a TECkit mapping for the
IPA characters (which I'm willing to do, but only if there are no
other options).

Has anyone run into this problem before? Can it be solved by some
combination of \protect, \expandafter, etc.?

Sincerely,
Andy Lin