The applications is web based (php). I have managed to stabilise the database:

The error in log file was:

Autogrow of file ** in database ** cancelled or timed out after 3344 ms. Use ALTER DATABASE to set a smaller FILEGROWTH or to set a new size.

Having monitored the saze of the data file it hasn't really grown recently. It's 18GB in size but has been for months. I'm not sure why this has suddenly become an issue?

I set it to 2% and all seems OK. Could this be a hardware (although there is plenty of free disc space) / memory / processor issue?