oops, we're in the webchart newsgroup but this question is about winchart. i'm going to move the thread now. but first, to answer your question... this issue with UltraPopupControlContainer was fixed and is pending release in a hotfix.
the bug # is BR30578. it is fixed in these versions: 6.3.20063.1090 CLR 1.x, 6.3.20063.1090 CLR 2.0,
7.1.20071.1066 CLR 1.x, 7.1.20071.1066 CLR 2.0, 7.2.20072.1074 CLR 2.0,
7.3.20073.1048 CLR 2.0, 8.1.20081.1005 CLR 2.0