Not sure if this has been identified by other users or not but (rarely) when I open some older projects, all of the BUSS names are not available in the drop down menu.  Once I see this, I know I am in trouble because this situation is a co symptom of another problem, that is:  adding FX to buss tracks leads to a "SONAR NOT RESPONDING" situation.
 
Don't know what causes this and like I said, it happens rarely but it just happened to me again on an older project.  Don't know what causes this and it happens only when I have 12 or more busses (give or take a buss or 2).
 
Any insight on how to fix this within a project?
 
Thanks,
Jim
 

You could try deleting the bus that isn't "visible" to the sends menu and re-create it.

Can you share a copy of such a project file somewhere?

Bristol,
 
Thanks, tried that and it doesn't work.... it is like the mapping to busses is screwed once it starts.
 
Jim
 
PS Mr B, not sure that posting a project file without the PLUGINS on your side is going to work. I could do a screen capture and try to post that somewhere... where I show the busses and the buss insert drop menu with the missing buss.  At this point, I have already deleted the missing buss and recreated it, so the busses show up but inserting effects into the busses only causes the NOT RESPONDING message.   Adding FX into tracks works fine.  It is odd and it has happened to me on about 4 or 5 projects throughout history (which isn't a lot but enough to be irritating).