Have you seen my new function generator

Was testing the BoSoZ on the bench, everything was looking perfect, when it suddenly developed a 5MHz oscillation. I mean, it really looks like I designed it for a nice clean sine wave at 5MHz. Very annoying, and I have no idea why it would be fine then develop this problem. I'm willing to believe the power rails are ringing, but they looked clean to me.

Very annoying, and now I'm going to bed. Harumph.