rundll.exe is not a service. It is used to load programs (the "main"
function) from DLL files, so you will see something like "rundll.exe
<progname>,<parameters>".
If this occurs during startup, check your registry Run keys to see if
one of the startup programs has an invalid command line. If it is an NT
service, stop all the non-critical ones and start them one by one until
you see the message again. Check its properties for the command line
used to load that service. I didn't find any of my NT services that
used rundll.exe, so I suspect it is a startup program in a registry Run
key or in the common or your Startup group. You can use msconfig.exe
(borrowed from Windows XP), Mike Lin's Startup applet, or SysInternal's
AutoRuns to see those.
mstask is the Task Scheduler. Check NT services to see if it is
configured to start automatically. I suppose it is possible that it
calls rundll.exe or maybe you have scheduled events in Task Scheduler
that use rundll.exe to execute timed or startup events from there.
