Neutica+ doesn't like Bullet Proof Security it seems. When BPS is configured, you can't assign featured images or delete plugins for example. BPS doesn't break my other themes on the same server (although none of these are based on Thematic come to think of it), and the BPS developer, AITpro, is nonplussed too.
See this thread from the first mention of neutica+
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Thanks for the prompt response Allan.
BPS is, I think, the leading way to lock down a wordpress instance by setting .htaccess appropriately, so this is a bit of a major problem.
AITpro did propose testing the combination in the tread I linked to above if you'd provide them with a copy of Neutica+.