Most people are under the mistaken notion that the common surge suppressor (i.e. the ones that use MOVs (Metal Oxide Varistors)) lasts forever. They don't.
Every time a voltage spike is suppressed by the surge suppressor its useful life is reduced (i.e. the MOVs lose some of their ability to suppress voltage spikes). Eventually the MOVs become useless and are unable to suppress any voltage spikes and what you're left with is just a plain old power bar.
Some surge suppressors will warn you when the MOVs aren't functioning anymore (i.e. usually by indicator LED(s)).
I would say your surge suppressor has done its job (i.e. served its useful life) and its time to get a new one.