shell escape causes vi to lock up

[J Q Johnson]

A frequent cause of hanging in deeply nested process trees is exceeding
your max process count.  Check the entry in the AUTHORIZE database to
see if that is your problem.  In the scenario you describe, you have
only cshell + vi + sh + command, but an analogous situation is a command
in readnews like "s |mail someone" which uses cshell + readnews + sh
+ mail + a whole host of mail subprocesses.  I find that I need a process
limit of at least 10 to do much of anything under Eunice.  Another possible 
limit you might be hitting is BYTLM.