Database – Event ID 7888 : Transaction Log for database is full

My application is running in the SharePoint Servevr 2007 environment, however I was encounter an error as below:

"A runtime exception was detected.
Details follow. Message: The
transaction log for database 'XX_DB'
is full. To find out why space in the
log cannot be reused, see the
log_reuse_wait_desc column in
sys.databases

Techinal Details:

System.Data.SqlClient.SqlException:
The transaction log for database
'XX_DB' is full. To find out why space
in the log cannot be reused, see the
log_reuse_wait_desc column in
sys.databases at
System.Data.SqlClient.SqlConnection.OnError(SqlException
exception, Boolean breakConnection)
at
System.Data.SqlClient.SqlInternalConnection.OnError(SqlException
exception, Boolean breakConnection)
at
System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject
stateObj) at
System.Data.SqlClient.TdsParser.Run(RunBehavior
runBehavior, SqlCommand cmdHandler,
SqlDataReader dataStream,
BulkCopySimpleResultSet
bulkCopyHandler, TdsParserStateObject
stateObj) at
System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader
ds, RunBehavior runBehavior, String
resetOptionsString) at
System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior
cmdBehavior, RunBehavior runBehavior,
Boolean returnStream, Boolean async)
at
System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior
cmdBehavior, RunBehavior runBehavior,
Boolean returnStream, String method,
DbAsyncResult result) at
System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult
result, String methodName, Boolean
sendToPipe) at
System.Data.SqlClient.SqlCommand.ExecuteNonQuery()
at
Microsoft.SharePoint.Portal.Analytics.Processing.UsageDataProcessor.processSrpUsageData(SharedResourceProvider
srp) "

The SQL log was filled up large amount of space within 2 days.
I've tried to move some of the unused/testing database to another drive to free up some space, but unable to do that because the LDF files was used by another program.

How can the log being fill up so quickly? Please help to fix it, thank you.