"I'm getting an error when first test is mocking a class, and then another test is using this class in a regular way. The class turns out to be mocked in the second test and fails with unexpected invocation."
Sounds to me like either of the following might be true:
You've created a mock dependency that you've added to a factory, so it's always returning this mock dependency
You've used power mock to prepare a class for test and this has persisted between your tests.
If either of those are true, or something else has occurred, I would suggest that there is a design flaw somewhere in your code base.
If option one has occurred (which it can when testing factories that return singletons for example) then it is the job of the individual test class to ensure that the mock dependency is replaced after it has finished with it.
If option two has occurred, then perhaps you'd actually like to use the @PrepareOnlythisForTest
Ultimately, what you're looking for should never be needed.
Remember to always mock responsibily.