Lost performance history when install syslog server

One month ago I set up a syslog server in vma as per this post: http://www.simonlong.co.uk/blog/2010/05/28/using-vma-as-your-esxi-syslog-server/

If while in advanced performance tab for any VM or host I specify and date range (1 week, 1 month), I get a graph that has blank data for the period of time that I have had my syslog server set up.

Advanced perf in real time works fine, and strangely view performance via 'overview' works fine for both real time and history.

I thought perf metrics would be stored on the database but apparently not...?  Maybe a coincadence?

Thanks,

Jaime