I'm using IB 2.3 on OS4 & haven't had any problems.
Is it by any chance a 'lenghty java script' type error.
If so, this is because some java scripts can be complicated & on a slower (Classic) machine IB might appear to have locked up when it hasn't, so you get those messages up. You can change the java timeout value in the settings.
If it isn't, you've got me.
FuZion.