>This is from my fading EE knowledge, so it may be a little off.
>Anyone chime in if they have a better memory than this.
>
>VA=Volt Amps
>Watts=Volts * Amps

Here's the scoop.  Watts = Actual power consumed.
VA = (RMS volts) * (RMS current).
If the voltage and current are in phase with
each other than VA = Watts.  If they are not (and they
usually aren't) than VA > Watts.  What this means is
that if your computer consumes 100 Watts, you actually
need something with a higher current rating than what
you would calculate by dividing watts by volts.  Hence
the common use of VA.  If your computer just gives a 
current rating then multiply by the line voltage to get VA.
So, 3A, 120V = 360 VA

>"VA" is the AC equivalent to the DC "W" for Watts (electrical power
>consumption). You need to distinguish because you usually have inductive or
>cappacitive consumers (did I get the translation right here?). You may want
>to ask an electrical engineer for details.
Watts are the actual consumption, but VA tells you what your source
(outlet or UPS) must be capable of.  With computers, its not just
the inductive/capacitive nature , but the nonlinear nature of the 
load (but thats for another place).  Its not uncommon for a computer
to require a UPS with VA rating as much as twice what the actual
power consumption is.

For a UPS, there should be 2 specs.  The first would be VA.
The UPS _must_ be rated at more VA than the computer (otherwise
you'll blow fuses or get smoke).  The second spec should be called
back up time or something like that.  A typical spec might be
280 VA
Backup time 17/5 min  (half/full load)
Note that the relation isn't exactly linear btwn life and load,
but it will give you an idea.

Hope this helps.
Dan