Only works if I disable some categories - seems to have exceeded a limit

Issue Summary

My profile CSV has been working ok - but then stopped two days ago, after about 15 seconds it goes to a browser page.

If I disable some of the categories it works again, the client wants all the data tho and more users will subscribe yet (an exhibition in July)

there are 33 users in the database
there are 25 categories for each user

Many thanks

Kimster