I am pulling my hair out with this particular problem... Right. Longtime Logic user. I have been running Express 7 with an M-Audio MobilePre for ages now under Tiger. Recently updated to Leopard and my M-Audio Interface (latest driver installed) was routinely crashing Logic. I was getting a recurrent error message "Error synchronizing MIDI and Audio", after which I would not get any output from the interface. Grumble, grumble. I uninstalled, reinstalled, checked the interface compatibility with other programs etc. Device seems to work alright under 10.5.2 for most core-audio stuff (iTunes, Quicktime, system sounds et al.) but I get neither input/output under Garageband, and the above error message in Logic. I've done a bit of hunting around on the internet and it seems that M-Audio are being pretty slow in updating their drivers. The most up-to-date one is for 10.5.1 and there is no indication from them as to when a patched driver for 10.5.2 might be made available. Seems like a fairly simple driver issue, doesn't it? Here's the twist... I upgraded to the new Logic Studio. I left my old version of Express and Garageband installed and installed the new Logic Studio. Without any tweaking the set-up worked flawlessly. The error message I was getting previously didn't show up and the whole thing was smooth. For the last few weeks it has been great and I quickly forgot about my previous problems. But another twist... Today though, I opened Garageband with the M-Audio device plugged in and since then the "Error synchronizing MIDI and Audio" message has returned. I've uninstalled and reinstalled Logic and all its components and its still happening. I've done the same with the driver. No dice. My question to you guys is: what has opening Garageband done to my audio set-up that would have destabilised Logic and reinstated this error message and fault? I'm at my wits end. I'm halfway through demo-ing a bunch of songs, I'm going away to record in a couple of weeks time and need to get these mixes finished. Any help would be greatly appreciated.