Hi tnproperty, I was having the same issue as you after updating to Mavericks.
I came across the solution that worked for here - have a read through: http://www.ctimls.com/Support/KB/Error Fixes/Fix_Silverlight_issues.htm#Enable Silverlight
1. Open Photosynth.net in new Safari tab
2. In the top left of Desktop, next to Apple icon, click 'Safari'
3. Under Safari select 'Preferences'
4. Select Security
5. Click on the 'Manage Website Settings' button
6. Click on Silverlight in the list of available plug-ins on the left
7. On the right, select the Photosynth website
8. Click 'Run in Unsafe Mode' (to give Silverlight unrestricted access to computer resources when running at the Photosynth website.
9. Beside 'When visiting Other sites'
Select 'Allow'. Or 'Allow Always' only if you intend for all websites to be allowed to use the selected plug-in.
Do not select 'Run in Unsafe Mode'
10. Click Done.
11. Quit Safari & then Reopen, and go to photosynth website