weird \mathrm error

[Manoj Rajagopalan]

hi all

  I'm getting this strange "\mathrm allowed only in math mode" when my 
appendix chapters contain equation arrays. This is a latex error and 
also happens when I export to latex and run latex on the file.

  Would someone be familiar with cases when this comes up? I ran chktex 
on my latex file but I got only warnings, no errors. So I'm guessing a 
mismatched '$' is not the cause.

Thanks,
Manoj