Enabling THold causes Cacti not to record graph data

[Ryoga]

Weird one here. I've having trouble with the thold plugin 0.5 on Cacti 0.8.8b. Whenever I enable thold in the plugin management, Cacti stops recording data for the graphs. If I disable thold, graphs are showing data as normal. 'Current / Average / Maximum' figures still hold their units and big gaps in the line graphs when I activate thold. There are no known errors in the log files - enabled debug on both thold and cacti.

I've also tried a few solutions on these forums (i.e. changing number in setup.php, setting authentication, etc), with no success. I'm rather baffled. Any ideas?