There will be a javascript error and no way for you to pick the value that you want, because MOSS decides to help you by adding a input text field used for looking up your value as you type and emulates an select box picker, by positioning a layer containing filtered values.
The positioning fails because the the input text box is nested in a table and the offsetParent/offsetLeft/offsetTop are failing (known IE bug).
So in the core.js there are two functions AbsLeft and AbsTop which you'll have to override in order to get an aproximate positioning.