Online status not functioning

Hi,

I have a problem with modlos in that the Online/Offline status is not updating when avatar logs on or off a grid. All other functions (including correct updates of last login in Avatars list) work well.
The environment in this case is as follows:

Windows Server 2003 64-bit + xampp 1.7.3
Moodle 1.9.12+
Modlos 1.5.5 NOSL
opensim 0.7.1.1

This is not a fresh install- original moodle version on this server was 1.9.10, modlos was 1.5.0 nosl, opensim 0.7.0.2

I have tried the following:

Executing the "clear login information table" from the management tab
Reinstalling the modlos block

Is there something specifically I can look for at the database or code level to see why this is the case or any other particular information I can provide that may give you a good clue to troubleshoot this?

cheers,
Adam

PS: I am thinking of those of you whose families were impacted by the tsunami and after-effects and hope that their journeys of rebuilding are going OK.