Error in the graph

I have a weird error when click on graphs for all Windows hosts.

pythonThresholdException User-supplied Python expression (here.getTotalBlocks() * .9) for maximum value caused error: ['usedBlocks_usedBlocks']

By default when you assign a host to FileSystem template (in our environment it's always Windows for whatever reason), there is one graph for storage usage utilization. It has a formula in the maximum threshold value which is referenced in the error.

Any ideas?

SNMP is working. I've tested usedBlocks OID.

Thank you.