Randomly I got a "An unexpected error as occurred" when I try to open some .ACD files. This strange thing also happens with the backup file. There's no any other information so I don't know how to solve this. The project file simply becomes unusable. Can anyone help?
I'm not sure what could be causing this, and the only work around i can think of (reinstalling the previous build and re-saving the file) may not work. So I think your best bet is logging a support ticket.
(alternatively, if you forget that URL in future you can find it by browsing to magix.com, logging in, hitting support, clicking making support requests)
log in to the support portal
click Do you wish to contact technical support -> music -> enquiry about acid pro 8