ReadUncommitted broken in SqlLite against NHibernate

[Pat]

I am using sqllite for test cases in a project that leverages
NHibernate. Everything is working great, except when I try to create a
ReadUncommitted transaction:

e.g.
Session.BeginTransaction(System.Data.IsolationLevel.ReadUncommitted)

The error message is: "isolationLevel" (thats it)

The call stack looks like:

at
System.Data.SQLite.SQLiteConnection.BeginDbTransaction(IsolationLevel
isolationLevel)
at
System.Data.Common.DbConnection.System.Data.IDbConnection.BeginTransaction(IsolationLevel
isolationLevel)
at NHibernate.Transaction.AdoTransaction.Begin(IsolationLevel
isolationLevel)

If I switch to a different isolation level (like serialized or
readcommitted), everything executes correctly.

Ideas?

NHibernate 2.1.2
SQLLite (.NET version) 1.0.65.0
Fluent NHibernate 1.0