CSS Alignment Issue with my CSS Rendered Calendar in IE8... Struggling to see what's wrong...

What've I done wrong...? See what's happening with my calendar here (I would C&P the source but it also has the entire php & javascript queries in it, so best if you check it out direct at site):

http://www.tuirennhurstfield.com/calendartrial.php

In IE8 the SUN & MON columns are replacing columns FRI & SAT and are pushing TUES-SAT down a level so they are below... This seems to only be happening in IE8, works fine in IE6, IE7, Safari and Firefox...

I purchased this script and the script worked fine in IE8 on the demo (see here: http://www.codecanyon.net/item/smooth-php-calendar-reloaded/full_screen_preview/105891 )

I've clearly edited something wrong in the CSS when I was making it work with the visual look of my site... But I'm not sure what I'm looking at, and the original developer has given me the sterling advice of "check your css", which given I did not edit any parameters only font size, type and colours I am now baffled...

If you can help at all please let me know...

I've attached the CSS file

Thanks!!!