Try installing the “Use Google Libraries” plugin. See if that fixes it.
If that works, then you’re having javascript compression issues. The plugin (among other things) disables that piece of 2.8.
The new release of 2.8.1 will have some changes to correct the compression problems, for people who have the issue (it’s relatively rare, only happens with certain servers and browsers, etc).
On a side note, if an upgrade is going to make you “lose money”, then I would recommend TESTING before installing new software first. Any shop that depends on a piece of software needs to have some form of quality control in place. WordPress is free software, no warranty. If it breaks, then that is your problem.
So next time, have a test site up and running to upgrade and test first, before you upgrade your main “money-making” system, yeah?