Thank you for posting in our forums! I'm sorry to hear you are having issues with connecting to the correct Slingbox in your Directory. This may be happening because both models currently have the same public IP address. They will need to be different. Your router assigns this automatically, it should not be giving the same IP address twice. I would recommend resetting either the SOLO or PRO-HD to factory settings and then going through the online setup assistant again. This may assign the Slingbox a different IP address. Below is a link to an article that will tell you how to reset the Slingbox to factory settings. Feel free to reply to the post if there are any further question or issues.
Hope this helps!
The Sling Moderation Team