Personally I think it's ok to mention a "technical problem" as a generic phrase but try to stay away from words such as Hydraulics, Engine Failure, pressurisation etc etc. And when it comes to weather, I try to avoid terms like thunderstorms, windshear, tropical storms, cross winds or anything else that might spook the pax.
Easier said than done sometimes but my opinion is that it's a case of a little knowledge is a dangerous thing when it comes to how much the pax should know.