First there are no known issues with IE9 versus IE8 with regard to selecting from a drop down. Sometimes we do see the application itself detect which browser version it's running in and behave differently. So this behavior could be application specific.
If I can get direct access to the application or if you can send me a Fiddler trace of the application running normally in IE9 (no Test Studio involved) then I can troubleshoot why it's not behaving as expected.
Regarding the compile error, I cannot explain why you're getting it. I just verified this small code snippet compiles perfectly here:
ScratchTest2 : BaseWebAiiTest
"New Coded Step"
HtmlSelect DropDownList1 =
Which version of Test Studio do you have installed? We did change the name of these methods in version 2012.2.1204
. They used to have upper J in them and now they have lower j in them.