Are you out of all other screens? If not, the system will do just what you have mentioned.
 
Other possibility is that security is not set for PO-L (which is the primary program) and IN-B accesses.

When you first start DBA and the "This program is registered to..." license screen comes up, DON'T click the X to close it.  Press Enter or any other key or wait for it to close itself.
 
Screwy as it seems, clicking X to close that screen messes up any programs that are chaining to another program and then back to the original program which is what is happining in IN-B.
 
The other issues mentioned about having other DBA windows open at the same time is also an issue but if you only have IN-B open then I bet it is the license screen.
 
Both these issues are fixed in TAS 6 Evolution.