I'm getting a System.ArgumentNullException while in Preview or Experience Editor.
I have since pointed a blank instance of Sitecore (8.1 update 3) to the dbs and can replicate the issue but cannot find the root cause:
From the trace it would appear that the issue is access related - the item cannot be read by the current user. However, I cannot identify any items that have security on them for the user (admin).
I have run the SPE report to find items with security on for the user but this yields no results.
Are there any other areas I can investigate here? Please ask if you require additional information, I am fairly new to Sitecore.