Lately I have been noticing a squeak in my engine bay while driving. It only happens in two circumstances...

1) around town, once i get up to about 30 in second gear and shift into third. I will let the clutch out all the way then there is a squeak and I feel the car loose a little power for an instant.
2)While just cruising at constant speed, i will hear the same squeak and loss in power, that will happen about every 30 seconds to a minute.

I thought it might just be a loose belt, but they all seem tight. It sounds like its coming from the front drivers side section of the engine bay. Any help would be great! Thanks!!!