ASPxComboBox in Sharepoint (WSS 3) with IE7

Hi,
I'm developing a (asp.net) web part with an ASPxComboBox inside it.
When I use this web part in Sharepoint (WSS 3) and set its width and/or height to a fixed size, the drop down list appears away from the combo. If I don't set the width and height, it works fine.
This only occurs when the web part is under wss3, when the web part is placed in an asp.net page everything works fine even when the web part has a fixed width / height.
There are another two points:
1 - The same thing happen using the ASPxPopUpControl, no matter how I set the PopupHorizontalAlign and PopupVerticalAlign;
2 - Using FireFox 3 this issues DOES NOT happen.
Please see attached a sample project and the steps to reproduce.
Thank you,
Bill
Steps to Reproduce:
Using IE 7, do the following:
1 - Compile the sample project and copy the ComboInWSS.dll to the _app_bin directory of WSS 3;
2 - Add it to the safe controls list in the sharepoint's web.config:
<SafeControl Assembly="ComboInWSS, Version=1.0.0.1, Culture=neutral, PublicKeyToken=null" Namespace="ComboInWSS" TypeName="*" Safe="True" AllowRemoteDesigner="True" />
3 - In wss3 site, go to Site Actions -> Site Settings -> Web Parts and add the ComboInWSS web part to the Web Part Gallery
4 - Go to any page in wss3 and add the ComboInWSS web part to the page
5 - Click on the combo's drop down button and check that the drop down list shows as expected
6 - Click on the ComboInWSS web part menu (small arrow in the top right corner) and choose "Modify shared web part"
7 - Set the width and height to any value (for example choose 300px for height and 450px for width)
8 - Click in apply and the click on the combo's drop down button
Actual Results:
The drop down list appears in the lower right corner of the web part, far away from the combo.
Expected Results:
The drop down list should appear bellow the combo.