fileUpload not working on IE

Hi!!
I'm having trouble with Internet Explorer file upload.

I have the following code:

   aCanvas fileUpload
        id: 'fileUpload';
        class: 'invisibleFrame';
        accept: self allowedExtensions;
        callback: [ :aFile | self halt. file := aFile ]

The problem is, on Firefox i get the Halt message and "aFile" is a WAFile, but on Internet Explorer i never get the Halt message, and when I continue processing the upload, I don't have the file!

I have that upload form inside a jQuery Modal Dialog, and the form is not nested within another form. It's set as multipart targetting an iFrame.

Has anybody faced this issue before? How did you solve it?

Thanks in advance!!
Alejandro