Are you using S to the TV or the Slingbox (or both)?
You should be using component for the Slingbox Solo. It has a loop-through if you're using component for the TV as well.
The message warning about SD is more likely coming from the HR34 as opposed to the Slingbox. The new "HD GUI" doesn't display on the SD outputs unless you've chosen an SD resolution. Instead you get a message similar to what you describe.
Again, component is probably your best option (unless you get stuck with a protected program)
To get you going, try telling the Slingbox you have an HR22.
How are you accessing your Slingbox?
You should be using component for the Slingbox Solo. It has a loop-through if you're using component for the TV as well.
The message warning about SD is more likely coming from the HR34 as opposed to the Slingbox. The new "HD GUI" doesn't display on the SD outputs unless you've chosen an SD resolution. Instead you get a message similar to what you describe.
Again, component is probably your best option (unless you get stuck with a protected program)
To get you going, try telling the Slingbox you have an HR22.
How are you accessing your Slingbox?