Host mouse not getting locked with DomU guest on vncviewer

[Mayuresh <mayuresh%acm.org@localhost>]

On NetBSD 8.0_RC1 amd64 Dom0 with Android x86_64 live CD as hvm DomU:
Using latest net/vncviewer, I am unable to move the guest's mouse pointer
without dragging it (i.e. have to keep the left button pressed to drag the
guest mouse pointer wherever needed).

I did not face this on WinXP guest with more or less similar conf file.
Have used the following as instructed somewhere for smooth functioning of
mouse.

usbdevice = [ 'tablet' ]

Tried switching to fullscreen. But then the screen goes blank. Refresh
screen also does not restore it back.

Is this a vncviewer's problem or xen's or guest's and what can I try to
work around this?

Mayuresh