This behaviour has been reported on Pro Tools 9.0.2 and observed on Pro Tools 10.
Pro Tools fails to open a saved session, with an error message stating that it is not able to set the sample rate (even though it is already set correctly for the SSL audio hardware).
There is a workaround which is to create a new session at the sample rate of the existing one you want to open. Once the new session has been started, you should be able to open the saved one.
If you then change the sample rate of the SSL hardware to open another existing session that has a different sample rate, the problem may happen again. The same workaround can again be used.
After this, Pro Tools should be able to open sessions at either sample rate without further error messages as long as the SSL hardware's sample rate is set correctly first.
Please refer to Avid technical support if you require further details about or help with this.