EXISTS Clause Failure vs IN

Under Collections Administrator | Administration | Manage Queries, run a search to find an existing query. Then, Update. If I enter a query that contains a SQL exists clause, then after I click Apply I immediately receive a browser message that "the connection was reset". If I use an IN clause instead of EXISTS then no problem.

It is as if the EXISTS clause is not supported. Is this true? Or maybe it is a bug and whatever seeded mechanism is parsing my query is aborting.