problem using screen after running /bin/su

[Edward Quillen]

i have certain accounts there that can only logged into using su - 
<username> instead of a direct
login (solaris 9).

when i attempt to run screen (v3.9.15) after i have run su - <username> 
i get the following error
message:

Cannot open your terminal '/dev/pts/4' - please check.

can you think of anyway to get around this short of logging into the 
account directly?

i have tried running   exec /bin/su - <user>   and it still didn't work.

thanks,
ed
address@hidden