> What kind of reason could that be?
A bug in your code.
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program[/url] (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
And don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags[/url] so the code retains its original formatting.
> When part of the popup of the combobox is ouside the container, it
> will be freezed. Otherwise, it won't.
What part of "create an SSCCE that demonstrates the incorrect behavour" is so hard to understand?
Works fine for me in this SSCCE:
http://forum.java.sun.com/thread.jspa?forumID=57&threadID=688505&start=3
Sorry about not listing the code. I have made some short simple codes to test the JComboBox. They all work fine. But my project is very huge and it is very hard to extrect the problem part out of it. So I just wondering if it is a common problem with common reason.
Sorry for any trouble I have made.
> So I just wondering if it is a common problem with common reason.
I've never seen it before.
It's not a common problem as you've proved by creating a simple program without any problem.
So its a combination of something you are doing in your more complex situation, which you need to debug.