OK, here you have it from SNOPES:

Boil on Troubled Waters

Claim:   Water boiled in a microwave oven can suddenly "explode."

Status:   True, but rare.

Example:   [Collected on the Internet, 1999]

Microwaving Water to Heat it Up

I feel that the following is information that any one who uses a microwave 
oven to heat water should be made aware of. About five days ago my 26-year 
old
son decided to have a cup of instant coffee. He took a cup of water and put 
it in the microwave to heat it up (something that he had done numerous times
before). I am not sure how long he set the timer for but he told me he 
wanted to bring the water to a boil. When the timer shut the oven off, he 
removed
the cup from the oven. As he looked into the cup he noted that the water was 
not boiling but instantly the water in the cup "blew up" into his face. The
cup remained intact until he threw it out of his hand but all the water had 
flew out into his face due to the buildup of energy. His whole face is 
blistered
and he has 1st and 2nd degree burns to his face which may leave scarring. He 
also may have lost partial sight in his left eye.

While at the hospital, the doctor who was attending to him stated that this 
a fairly common occurrence and water (alone) should never be heated in a 
microwave
oven. If water is heated in this manner, something should be placed in the 
cup to diffuse the energy such as a wooden stir stick, tea bag, etc. It is 
however
a much safer choice to boil the water in a tea kettle. Please pass this 
information on to friends and family.

Carol's conclusion:  Yes, it can happen but probably not as regularly as the 
doc was suggesting!

I think it's more likely with substances added (part milk and coffee, 
perhaps, though I have no proof of that).  In our case I definitely think it 
could have been a problem with the glass mug - so I'm saying the utensil 
used may have a bearing.

Go figure!  I'll go back to sleep!

--
Carol - Reading, UK

To you, o Lord, I lift up my soul;
In You I trust, o my God.  . . .."  PS25:1-2 NIV.



----- Original Message ----- 
From: "Phil Scovell" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, August 30, 2006 7:48 PM
Subject: Re: Fw: HEATING WATER IN A MICROWAVE - Caution


> This is one to look up on snopes I guess but I have heard of this before 
> and
> things falling apart after being super heatened in the microwave.
>
> Phil.