What sort of problem is altered mental status?

Confusion. Altered mental status is just a medical term for "confusion" which can be caused by a multitude of things. Anything from an infection, to drugs, to electrolyte imbalances and organ failure can all cause altered mental status.
Confusion. A change in mental status usually refers to a person who is confused in some way, though this could also refer to any change in how a person usually is/thinks. Even sleep is technically a change in mental status!