Table headers always visible

I am using the solution provided here:

HTML table headers always visible at top of window when viewing a large table

The problem is, my table is filled with information pulled from a db, and as such I have little control on how "long" something is. So my headers have lots of extra space around the title.

This is no problem until I scroll down, when all of a sudden all the headers lose the auto-inherited size and all of a sudden do not align with the rows.

How ca开发者_JS百科n I solve this issue?