I'd start with the typical backup stuff... (grain of salt, I've never used LMI Backup)
1. Are you doing flat-file backups, or are you doing system-state, etc., as well?
- if system-state, etc., do a "vssadmin list writers" in elevated Command-Prompt and make sure they are all in Stable and ready states, troubleshooting as necessary.
2. Have you recently done any file reorganization which would maybe make the list defined in the "selection definition file" invalid? If so, if you remake the list does the backup succeed?
3. Since you mention several SBS2011 installs having the same issue, I am wondering if there's something in the event logs indicating a problem, or if Server Backup is set up on those servers, etc.
4. Does the user account that is logging in as the service (presumably it's a service) have access to the data being backed up as well as the folder where the "selection definition file" is located? Once again the event viewer should be showing errors here, although it wouldn't hurt to check the Log On As section of the LMI Backup services. (*edit* note that if you are backing up data from other PCs/servers than where LMI Backup is installed, the service will need to run as a domain administrator [or equivalent] or Network Service.)
I have tried backing up a small file from scratch and this is the error in LMI logs.
================================================================ *** Report written on Wednesday, June 27, 2012 at 1:16:19 AM ***
Type: Backup Backup Set Name: WCA - Server
From Source PC: WCA (1) To Storage PC: Storage Server
Total Files Checked: 1 file New or Modified Files to be Transferred: 1 file Data Processed: 0 B of 20.78 MB Files Processed: 0 of 1 file Files Skipped: 0 file Data Transferred: 50.51 KB Backup Set size: 0 files, 0 B Number of Versions available: 0 Version
Started: 6/27/2012 1:06:32 AM GMT Ended: 6/27/2012 1:16:19 AM GMT Backup completion status: 2 Errors, 20 Warnings Duration: 0:09:47 Duration of actual file transfer: 0:02:37 Transfer rate: 329 B/s
Backup failed. First Error: Error [Disconnected - disconnect]