7.3 will not work

I have a 2 Ghz Intel MacBook pro with 512 Mb operating memory - and use an old MBox. I have had few small problems with Pro Tools 7.1.1cs but when I installed 7.3 - well the songs would open but they would not play - it said that I was overloading the USB and had to take out some plug ins - which didn't make any difference actually - I had checked the 'ignore error messages box'. Is it because I am using an older MBox? I deinstalled the 7.3 and reinstalled 7.1.1cs and everything is fine now... What am i doing wrong?? Thanks for any help...

I just bought an Mbox Pro to upgrade from an Mbox and also upgraded to 7.3 and I have the exact same problem - it won't play without showing an error message. Everything worked great before the upgrade. I'd like to go back to the previous software version but I don't know if it'll work with the Mbox Pro.

According to the digi support 7.3 should work with intel MBP and older Mbox. Have you tried trashing the Pro Tools preferences files, running disk utility and rebooting? Sometimes these steps are necessary when changing software versions. BTW, I've been a fan of your music for some time. Cool to be able to tell you that. Steve

also be sure you don't use any plug-ins that haven't been ported to universal binary - that can cause session problems

Lucky for the long weekend. After spending hours trying to get it running again (tried all the posted fixes) I uninstalled 7.3 and went back to 7.1.whatever - the version that shipped with the mbox pro. Even uninstalling was a long process. Now only every once in a while it locks up. I can live with that for now. Actually didn't have one lock up today and I was using it for hours. I also found my problem with the error message of "Mbox in use by another program". Once I removed the mbox from the midi settings, everything worked.