I configured TortoiseHg to use vsdiff as the default diff tool. When I try to diff my working copy against the current update, two single button dialogs open:
The first is titled "SlickEdit" with the text "No Files match these parameters"
The second is titled "Multi-File Diff Progress" with the text "Filtering files"
If I use Process Explorer from the SysInternals Suite, it appears the call to vsdiff has the correct arguments, but another call to vs with diff as an argument appends *.* to the first path. I'm assuming this interferes with correct operation.