Backup failed -

I get the following message when trying to run my normally scheduled backups.
SQL Backup log file
1/29/2008 5:15:34 AM: Backing up portal200401 (full database) to:
\\datadrive\SQL_Land\devsql02\portal200401_FULL_RG.bak

1/29/2008 5:15:34 AM: BACKUP DATABASE [portal200401] TO DISK = '\\datadrive\SQL_Land\devsql02\portal200401_FULL_RG.bak' WITH NAME = '<AUTO>', DESCRIPTION = '<AUTO>', INIT, COMPRESSION = 1

1/29/2008 5:17:23 AM: Thread 0 error:
Error 620: Error writing to backup file(s).
Process terminated unexpectedly. Error code: -2139684860
Thread 0 warning:
Warning 210: Error writing to backup file: \\datadrive\SQL_Land\devsql02\portal200401_FULL_RG.bak
Warning: System error code: (The semaphore timeout period has expired)

1/29/2008 5:17:23 AM: Server: Msg 3013
BACKUP DATABASE is terminating abnormally.
1/29/2008 5:17:23 AM: Server: Msg 3271
A nonrecoverable I/O error occurred on file "SQLBACKUP_EAED3D74-66F3-4463-9640-F7FE4758D53F:" 995(The I/O operation has been aborted because of either a thread exit or an application request.).
1/29/2008 5:17:23 AM: Server: Msg 3202
Write on "SQLBACKUP_EAED3D74-66F3-4463-9640-F7FE4758D53F" failed: 112(There is not enough space on the disk.)
1/29/2008 5:17:23 AM: Failed to close vdi.[/size][/size]



This was running fine and i have verified we have more than enough disk space available (214gb). I have received this type of error message in the past. does SQL BU default to the not enough disk when it receives other messages? Has anyone experienced this type of error?

Thanks
Geri