Steve,
I agree with Colin - In addition to his questions, is your backup-to-disk folder residing on the BE server itself or another machine? If the latter, you will need a remote agent license available for that machine to be able to receive the backups. Normally you'd have to have done this already for that machine's drives to even appear as an available path when creating a B2D folder on it..
Have you updated your BE server at all, and if so, the applicable agent(s)? Have you had any issues connecting to or querying the agent from your BE server? The error indicates that there may be a version issue, which could mean on of three things:
(1) You ran LiveUpdate on the BE server and need to update the agent(s) to match
(2) You installed a previous version of an agent on the target machine (i.e. installing a version 12 agent when you seem to be using BE 2010)
(3) You were using an older edition of BE and recently upgraded t0 2010 - to my knowledge you have to get replacement agent licenses when upgrading BE versions as the ones from the older revisions are no longer valid - Colin may be able to comment on that...
You can go to this site:
http://www.symantec.com/business/support/downloads.jsp?pid=15047
to get Service Packs / updates for your BE server (though using Live Update is generally easier). You can also get agent updates here, but if you're using Windows-based agents, there's a bit of an easier method. in your \Symantec\Backupexec folder you'll find RAWSBulkUpdate.exe. You can run that to check your agent connections and bulk-update them together. However, you may find this process hangs or times out if there are a lot of updates or if the updates are far enough behind that they need to be applied manually for the bulk updater to work right.
In that case, you can check your Symantec\Backup Exec\Agents folder, where you will find folders for each of the agent types. If your agents are runing on a 32-bit Windows platform, you'd want the RAWS32 folder for example. Copy the applicable folder to the machine your agent is running on, and inside is an 'updates' folder, with various .msp files (which are the individual agent updates). Run these on at a time (preferably in order - some service packs / hotfixes coincide, so you may want to double check the chronological order) and your agent will be brought up to the same revision as that of your BE server.
You can try again to use the bulk updater for future updates at this point, but be aware that you may have to manually update again if it doesn't work for ya.