What could potentially cause slow or poor coordination in an otherwise healthy and bright child?

Lot of options. Hard to say without more details about the child. Possibly a toxic exposure, infection or post infectious issue. Definately need to be seen and evaluated.
Specific impairment. Observation of individual variations has brought us to understand the complexities of development & movement. Some kids seem to lack position signals from their joints & extremities & must focus full attention on movements that others do smoothly. This yields awkward movements. This may occur with other motor issues or occur alone. Like dyslexia, the cause is unknown and progress is variable.