I too have this same problem, though strangely enough Spark used to work just fine. I’‘m using Wildfire v2.5.1 and Spark 1.1.4 (I first started experiencing the problem with Spark 1.1.3). I have all our users split-out into various shared groups which display just fine for me when using Pandion or Psi, but in Spark all my contacts are shown as being offline. Other people using Spark with our server (using similar configurations) aren’'t having this problem.
Looking at the Spark traffic window, I see activity where Spark asks for and receives data pertaining to conference rooms and transports, but nothing else. No errors or warnings appear in the Wildfire log files.
The only change I made recently was the installation of the pyAIMt transport, though Spark was working fine for a few days even after that was installed. I’'ve tried uninstalling Spark, completely wiping all its data off my local system (the Spark folder under Program Files and also the Spark folder inside my user folder under “Documents and Settngs”) to no avail. This is on WinXP Pro.