Huge Loading time due to 'too many' categories???

Hi Guys,

I am having a problem with a site im building. I have 90 categories (not really that many given ebay, gumtree etc have hundreds if not over 1000 each; with sub categories) but my site is slow slow as a result. It is most noticeable when you attempt to select a listing package.

So if you click > Add listing .. the page with all my packages come up in about 2 seconds.. not great itself. BUT when you try to select one of the listing packages there is a average 37 second delay!!!!! Needless to say the site is unworkable and unusable. I mentioned this to PP months ago when I started the site (just restarted it after a break) and mark looked at my site and said its because I have too many categories.

There are 7 main categories with between 3 and 20 sub categories. there are no third tier categories.

my questions are

1) has anyone else had this?
2) Does anyone think this is a problem or am i wrong to expect a classifieds theme to be able to cope with 90 ish categories?
3) $64 question …. does anyone know how I can fix this?

As ever, thanks guys