A bit late for the original poster, but maybe useful to others.
Two freeware viewers for structured storage files (including .suo-files):
https://github.com/ironfede/openmcdf (old URL: http://sourceforge.net/projects/openmcdf/)
http://www.mitec.cz/ssv.html (free for non-commercial use)
When you open a .suo file in one of these viewers, you will see streams related to:
- Bookmarks
- Debugger watches
- Unloaded projects
- Outlining
- Task-list user tasks
- Debugger exceptions
- Debugger Breakpoints
- Debugger find source data
- Open document windows
And much more…