I understand that ever since Comcast provided you with a digital cable converter, you keep losing channels.
The main issue is that the Slingbox SOLO is not capable to fix this issue, since it does not have a tuner. Your best option is to get the Slingbox PRO HD.
This unit have an internal tuner that might help you under these specific circumstances. However, keep in mind that it all depends on the signal encryption. If the signal you get is encrypted, you might not be able to get some of the channels.