http://bugs.winehq.org/show_bug.cgi?id=20392
--- Comment #8 from Mark I. pilota51@gmail.com 2011-10-28 05:47:14 CDT --- Still present in 1.3.31 with both IE7 and IE8, haven't tested IE6.
This appears to have something to do with a lack of support for XML/XSL/XHTML/whatever. I am mostly experiencing this problem with There which uses XML extensively for its pages. Instead of loading the file within the browser, it prompts to save the file without an extension and says "Unknown File Type".