Photoshop has an unacknowledged font limit.

The only known work around is to use a font manager and only activate the fonts you need.
This always the best way to work.

there are 5 font managers most people use.

FontAgent Pro - The majority of users around here seem to think this one is best. I am one of them. FAP is the most ATM Deluxe like. Auto Font Activation works perfectly for most, I've not heard any complaints.

Suitcase - this seems to be the next most popular. Auto Font Activation seems to cause problems for some.

Font Reserve - This app was bought by the Suitcase Folk. One of these days we are going to have Suitcase Reserve or whatever they call it.

Master Juggler - This is a relatively new app. The only review by a user over in the InDesign Forum, was, its not very good.

Font Book - This is built into Panther (10.3.x) if you have more than 200-300 fonts this is practically useless.

If you are wondering the exact font limit nobody knows because nobody actually has cared enough to count. If you have some spare time on your hands and you find out please post so we all know.