Site in 'Maintenance' mode- unable to remove

Hi,
I have just used the 'update all' to update all of the wpmu plugins.
The site now says it is "Briefly unavailable for scheduled maintenance. Check back in a minute."

I have not put it into maintenance mode, but assume the update of the plug-ins did this.

I cannot log in, as I just get the maintance mode issue. This is not an issue with the hosting, as other sites on the same host and server are working properly (pandora.mrhandley.co.uk for example).

How can I remove the blog from maintenance mode so I can log-in, and so visitors can visit the website?

Thanks,

Tim