Mark,
I had the same problem beginning with the install of Netbackup 4.5.  My 
problem, and possibly yours, was a Solaris 9 patch problem.  Once I patched to 
the recommended patch cluster, by Catalog backup went from 6-7 hours to 1 hour. 
 I would suggest the recommended patch cluster to see if that helps.
Chris

Hi there, Catalog backups are taking in excess of 4 hours to complete (often 
takes much longer.. up to 10 hours). We are running NB 5.1 on Solaris 9, 
connected to an ATL P7000 changer unit. The catalog is around 70 GB in size, 
with /usr/openv/netbackup/db/images containing aprox. 63 GB of data. Normal 
backups are functioning OK. Any hints as to why this is taking so long would be 
appreciated. Thanks, Mark