As I said, setting offline is completely the wrong solution. DO NOT try to take the DB offline, detach it or to restart SQL server.
What other messages are there in the log?
See the SQL Server errorlog for details.
This doesn't look like a full log file, it looks like a file is missing or inaccessible. What lead you to conclude that the log is full?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability