I understand that you are having some issues when connecting your Slingbox SOLO through powerline adapters. According to the provided information, the main issue seems to be related to the powerline bridges.
However, the fact that the computer gets a higher speed connection rate does not mean anything in particular. Keep in mind that the Slingbox will consume a higher amount of the available bandwidth, therefore, the computer will seem to take advantage of this situation.
The following links will provide you with some information that might help you to fix this issue.