Im assuming you haven't fixed your style-changing problem yet Barry?
Looks like there's something wrong with your browser. Maybe the browser itself, or an add-on that you are using.
I'm using XP with Firefox 3.0.6 (Latest version), and have no such problems with styles or this posting problem.
I only use 1 add-on for firefox- Foxmarks.
If anyone else gets any problems like this, please pot a screenshot, then I can look into it, but as it stands- Looks like it's a problem your end Barry.
What style are you using anyway?
EDIT: Another explanation for this error could have been that I was editing your thread title, therefore meaning the post you were replying to (With a naughty word in the title) never existed; hence this: