[jQuery] Table show/hide rows slow in IE

[gvido trepša]

Hi,
I have a table with 500 rows (7 tds each, and with lots of classes).  
They are all part of html document.
The menu has 10 categories, and clicking on the category is supposed  
to show only those rows where row's className==menu's categoryName.

Now, whether I do that by changing the display property of each row:
         'none'-->'table-row' || 'block',
or by setting the table's class name to the category name and adding  
the line:
         table .className tr.className { display: ...; }
to the style sheet, I have the same result:

In FF the table changes/redraws instantly;

In IE6/7 the change takes about 5 seconds, plus all other events,  
like hover etc. has a second or more long delay.

Any quick suggestions? Is this some known IE behaviour? Unavoidable?

--Gvido