WorkRave seems not to be detecting keystrokes on my second X display (:0.1)  
when I run it on :0.0. It does detect mouse movement properly. WorkRave does 
also seem to not detect button pushing on :0.0 (mouse), however it does on :0.1 
if I run it on :0.1. Error on startup: 
 
X Error of failed request:  BadAccess (attempt to access private resource 
denied) 
  Major opcode of failed request:  28 (X_GrabButton) 
  Serial number of failed request:  1833 
  Current serial number in output stream:  1834 
 
I tried running WR on both :0.0 and :0.1 simultaneously and enabling the 
networking support, however WR seems to be against using the ports that I 
specify, and in any event, it would get wiped out when WR writes its config 
out. 
 
Am I doing something wrong, or have I hit on a bug?

Please check if the record extension is enabled in /etc/X11/XF86Config-4:

Section "Module"
        Load    "record"
EndSection

Without record, workrave uses a dirty hack to monitor you keyboard.

Both workraves use the same configuration and the same port. You can also use
the environment variable WORKRAVE_PORT to define the port workrave must use.

I just tested Workrave with multiple screens (instead of Nvidia's twinview)

The hack only detects mouse movement, keyboard is not monitored; as you said.
The xrecord monitoring detects both.

I said this before: the hack will be disabled by default in the near future.

closing bug.