Thanks. I am rerunning the catalog jobs now but they are stuck in a queue behind a couple of backup jobs. Will get back with how they go.
From testing I ran this morning it would appear that we are having problems with all our Differential backups to the B2D folder but Incremental jobs are working fine. At the moment I can not be sure on cause and effect as they are backing up different data but hopefully I should be able to run a more conclusive test this evening.
It does not seem to be down to individual bkf files - there are several hundred and I have tested a random handful.