Some (most) cron jobs not running?

[SDB]

Hi

I've just written a cron job which writes a html file once a minute.

It funs fine from "run now" button, and shows correctly in the list for the next time its due to run, but doesn't actually run on its own.

On noticing this, I've checked the logs and it appears that lots of my crons (note, not crons written by me - this is my first) are not running, although some are running fine.

Any helps would be appreciated.

Simon