Rendering XML output (with large number of columns) to browser breaks

We have a stored procedure in our database which returns a cursor with over 400 columns. When we call the stored procedure from within the QT (using mode FixedQueryWithOutput), it renders just fine and very quickly in CSV format. however, when we attempt to render it (e.g. post it) as HTML format or XML format, it takes a very long time to render (even thought the results come back very quickly).

We are using the following specs:

OS: Microsoft Vista

Browser: IE (v7.0)

Java: Java 6, patch 20 (plug-in disabled)

Any hints/help would be greatly appreciated!