taking a shot here. in the modules directory there is an index.php file.
look at that file and see if there is an extra CRLF after the ?> closing php tag?
i had this issue on a site, where it was creating a javascript popup that was completely blank. so just check, or for a more bold move, rename the existing and replace it.
as a test, i renamed --> /modules/index.php to __index.php
then i clicked on one of the links from stats, i opted for Sites
the page loaded and said "Profile Not Available for View"
then named the index page back, and it loaded the sites.
so i think this may help. give it a try anyhow.
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