If I have help up and also open some other dialog 
(say Options) and open a secondary dialog from 
there, the help window suddenly jumps to other 
parts of the screen and resizes itself. 

I've seen this on my laptop, which has a 
relatively small monitor (this may be relevant). 

I've seen this in several scenarios, but here is 
one that reproduces for me: 

1. Start help from top level menu. It comes up on 
the right hand side and covers about 60% of the 
IDE, staying inside the bounds of the IDE. 

2. Open Tools > Options. The Help window is now 
hidden behind the IDE. Options comes up in upper 
left corner. 

3. Select "Ant settings"

4. Select "Additional classpath". This brings up a 
small dialog on the left, covering the options 
tab, but also fronts the help window, which shows 
up almost in the same location as before, although 
it's moved a little to the left so that the dialog 
and the help windows stick out equally much on the 
side and don't cover each other. 

5. Select "Add Jar/zip". A new dialog comes up on 
the right hand side. This causes the help window 
to come up on the right, much more narrow this 
time. 

I assume it was done to keep the help window 
visible, but the effect is a little disconcerting.
...