BACK UP FAILED ERROR.

I am finding below error in the Event3041 in the event viewer stating MSSQLSERVER.SQLServer2K8.LogBKUPFailed.Alert;  Desc: BACKUP failed to complete the command BACKUP LOG vivek but database is existing in the running fine. All jobs also executing properly. these are data i found in logs

C:\Windows\system32>(
md "E:\MSSQL\BAK\vivek"  
 sqlcmd -Q"declare @backup_file_name varchar(1000) set @backup_file_name = 'E:\MSSQL\BAK\vivek\vivek_'+convert(varchar(24),getdate(),112)+'_'+Replace(substring(Convert(varchar(24),getdate(),114),1,5),':','')+'_FULL.bak' declare @cmd varchar(4000) set @cmd = 'BACKUP DATABASE [vivek] TO DISK = '''+@backup_file_name+''' WITH INIT' if @@version not like '%SQL Server 2005%' set @cmd = @cmd + ', COMPRESSION' exec(@cmd) " 
 for /F "skip=3 tokens=*" %j in ('dir "E:\MSSQL\BAK\vivek"\*.bak /o-d /b') do (del "E:\MSSQL\BAK\vivek\%j" )
)
A subdirectory or file E:\MSSQL\BAK\vivek already exists.
Processed 203896 pages for database 'vivek', file 'vivek' on file 1.
Processed 5 pages for database 'vivek', file 'vivek_log' on file 1.
BACKUP DATABASE successfully processed 203901 pages in 10.412 seconds (152.994 MB/sec).

C:\Windows\system32>(del "E:\MSSQL\BAK\vivek\vivek_20110712_2200_FULL.bak" )