RC2-CFMX only able to upload .txt files

Juste wondering if I'm missing something silly. I have RC2 running on IIS6/CFMX. A little tricky getting the browser to work, but it all works fine now, except;
-I'm unable to upload anything besides text files....with all other file types FCK just hangs with the 'currently uploading file' above the fileField. If I close out and return to the browser, there is an icon indicating the image/file I just tried to upload with the paths all in place and correct....just no actual image/file. I've rumaged through the source without avail......any ideas would be greatly appreciated...thanks