http://softwareupdate.veritas.com/be/vxsdm/findnewupdates.jhtml lists that only be4691RSP4a_280008 is missing on our Backup Exec 9.1 installation.
If we download SP4a and try to install it, we get the following error message:
WARNING! The following patches need to be installed before this patch can successfully continue. Be4691Rsp1.exe
When we tried to install SP4 the error message is: WARNING! The following patches need to be installed before this patch can successfully continue. Be4691Rsp2.exe