Opening AA 2.0 MT Sessions in AA 1.5?

Okay, I'm a long time user of AA 1.5 and am excited about the potential of 2.0 (I'm still in the "trial vesion" mode but have pretty much decided to upgrade)...

Just curious why I get error messages when I start AA1.5 then try to open a project (that some tracks originally were recorded in 1.5) saved in AA2.0 form?

Tried to do that this morning and the message was something akin to "The number of tracks you are trying to open exceeds the limits of Audition 1.5"...Even though the original 2.0 session only had 7 tracks (no effects used)...

Any ideas? My primary concern is that while adjusting to the AA 2.0 learning curve, I will still be using 1.5 on occasions for projects that need to be completed in an expeditious manner...I'd hate to think that if I choose to experiment with AA 2.0 for a particular phase of a project that I won't be able to open if in AA 1.5 (without actually importing eash track individually)...

Thanks in advance for any help here?

Regards,
Papa

You can open 1.5 sessions in version 2.0 (depending on precisely what they contain) but you cannot open 2.0 sessions in 1.5.  When you do the first that's why you are invited to save under a new filename, so you don't lose the ability to open the original session in the original version.