We were running Confluence v 5.8.10 up until this weekend. After the upgrade to Confluence v6.3.3, I'm seeing this error on my pages. I have hacked at it and cannot find a work-around to get the table heading looking right.
Problem Definition: Before the upgrade my column heading font was white. After the upgrade it is black. I've drilled into the HTML and found that the div class tablesorter-header-inner is applied to the heading text whether or not the option for 'Enable Column Sorting' is enabled.
In the first image you will see the word 'Key' (red arrow) is my heading, and it is black, even though the CSS color attribute for the tr is white (and !important.--green arrow.)
In the second image you will see that the 'Enable column sorting' is disabled.
In the third image you will see that dark color is applied because the div class tablesorter-header-inner is in the base colors.css file with a dark color.
I think that the correct fix for this is for your code to not apply the div class tablesorter-header-inner when the 'Enable column sorting' feature is disabled.
wiki.homeaway.com, hidden behind our firewall. I think it is installed on Linux servers, but I'll have to get IT involved for any further details.