The standard versions of Pro Tools 9 and Pro Tools 10 allow for the use of a maximum of 32 simultaneous inputs/outputs. For this reason if your input/output count when using two FireWire Saffires exceeds 32, you will not be able to pass audio on the inputs/outputs with a count above 32. Despite this, these inputs/outputs will show up in Pro Tools’ I/O Setup.
To allow for the use of more than 32 simultaneous inputs/outputs Pro Tools 9 or 10 HD is required (which requires Pro Tools HD hardware).