Pro Tools 24 supports a total of 43 virtual disk tracks per d24 card, vs. 49 per Disk I/O card on Pro Tools III PCI systems. If a user creates a session on a Pro Tools III system, they may very well create a session that cannot open on Pro Tools 24. At the present time, Pro Tools does not properly protect against this situation, and you can get error conditions or crashes as a result (since the "illegal"session actually opens). The upcoming 4.1.1 release will add protection against a session mismatch occurring (by preventing the "illegal"session from opening). However, this will not resolve the differences between the number of virtual tracks available from the two systems. A workaround would be to use Track Transfer to split out tracks into a new session that is below the 43 virtual track limit in Pro Tools 24.Track Transfer can be used to create a session with a 'legal' number of tracks.