Has anyone had any issues with render.statement and the options.startdate and options.statement date? It says on the help and suiteanswers that they are of type date... yet when i put them in as a date object i get the wrong parameter - expecting a string... I try to put in a string (All different timezone formats) and i get unexpected error... NetSuite have had this case for weeks now and have been no help whatsoever as we only have basic support - so frustrating!!

I'm not sure if the format is determined by account preferences or not, but in our instance it wants strings in M/D/YYYY format, and definitely does not accept a JS Date. This is how we typically call it, which works in several scripts:

render.statement({ printMode: render.PrintMode.PDF, openTransactionsOnly: true, entityId: entityId, startDate: '7/1/2015' });

Thanks @scottvonduhn, turns out it wasnt an issue with the render.statement, but one of the corresponding workflow - i just hate the unexpected error and netsuite being so cagey about the issue! Thanks for your help!