Missing session vars when doing var_dump()

Hi I have come across a strange problem. I have an application that a user logs into and when I find the user in the database I load all the custom info for that use which I store. By the time I'm done, the session array has 18 key's. When I do a var_dump($_SESSION) I sometimes get 18 variables and sometimes I only get 16. The two fields that are missing are TEXT fields from a MySQL database and they also appear to be the last two keys when var_dump() returns all 18 keys. Does anyone know what is causing this, it's driving me crazy at the moment with many late nights. The PHP version running is 4.2.3 Regards Gavin Auckland, New Zealand