UBEC Voltages

I have noticed with a multimeter that the UBEC provides ~5.6volts when not connected. When I connect it to a 5V Arduino the multi meter shows ~5.25volts on the BEC output.

Using a computer PSU the 5V is 5V, connected or not. I know this all load related but can this be a problem in the long run?

I have actually fried 2 Arduinos, using 2 UBEC's. NOt sure if I am just being a puts and shorted something or is it the increased voltage.

Any device not outputing 5.0V +/- 0.25V is unsuitable. One that show that amount of voltage change between loaded/unloaded is not properly regulated.