Disappearing lines

I’ve been having a unusual problem that I can’t resolve.

Occasionally, I will have a line of numbers disappear AFTER the site loads. This is almost always when displaying a phone number. The page will load and instantly remove a particular phone number from the page.

This only affects firefox from what I can tell [running 3.6.2 currently]. IE/safari work just fine.

See the first example here http://www.stlphi.com and navigate to the contacts page. Watch the first cell phone number be removed.

Second example is http://springfieldmetrorealty.com/ and watch the cell and email address be removed.

I’ve tried to troubleshoot this, but any manner of editing they text on either site doesn’t seem to change the results. The cell phones still vanish…

Could I be missing an issue with firefox or could this still be my error within WordPress?