error message when uploading a pic

Hi Leah... got this error message tonight when i was uploading a pic into a post.

'The upload folder is full. Please try a smaller file and/or contact an administrator. '

The file wasn't that big... 18.2kb

It's not hugely important... just wanted to let you know.

Thanks Q-G, I've doubled the size of the directory so you shouldn't have any trouble now.

Thanks!