Sharepoint Error: Unable to complete this operation

We all know that Sharepoint moves in misterious ways, but well, I'm still a beliver. Today, one of our installations was throwing this error when trying to check-out a page:

"Unable to complete this operation. Please contact your administrator"

For debugging purposes, the message was less usefull than reading the coffee grounds. Hopefully, I searched for the error and the Google angel sent me this message.

"SQL Server has ran out of disk space".

First I thaugt it couldn't be my case, for the whole system would be failing, but then I found this message on the Sharepoint log:

Unexpected query execution failure, error code 9002. Additional error information from SQL Server is included below. "The log file for database 'XXXXXXX' is full. Back up the transaction log for the database to free up some log space."

And that was it. Mistery cleared. You can check what to do with a full transaction log here
http://msdn.microsoft.com/en-us/library/ms175495.aspx