In a new KB article, Microsoft has outlined reasons why a directory naming structure could cause ConfigMgr 2007 backups to fail. We’ve all had our issues with “special characters” when naming certain things in Configuration Manager, but the reason this one is important to note, is that even a backslash (“\) in the path name is considered a special character.
Microsoft’s example for no-no characters to use, goes like this:
So, be careful when giving your backup destination folder a proper directory structure name.
Read the full KB article (2748703): Backup destination folder of System Center Configuration Manager 2007 should not contain special characters