If you use Texts for "where" and "like" which are longer as fields in database, exception will be thrown. This doesn't happend if you are using "native SQL" whith the same DataProvider (in this case Firebird)
For an examlpe:
myItem.Name defined in database as varchar(5)
/* This causes none exceptions*/
[Test]
public void Can_DoLikeIfTextToLongUsingNativeSQL()
{
ISession session = this.OpenSession();
FbConnection conn = new FbConnection(session.Connection.ConnectionString);

string query = @"select * from ITEMS
where ITEMS.Name like '%1234567890%'
";

FbDataAdapter da = new FbDataAdapter(query, conn);
DataSet ds = new DataSet();

da.Fill(ds);

Assert.AreEqual(0, ds.Tables[0].Rows.Count);

session.Close();
}

/But the same thing with NHibernate, throws an exception/
[Test]
public void Can_DoLikeIfTextToLong()
{
IList<myItem> result;

using (ISession session = this.OpenSession()) {
using (ITransaction trans = session.BeginTransaction()) {
result = session.CreateCriteria<myItem>()
.Add(Restrictions.Like("Name",
"%1234567890%" /longer as field in database, causes exception, but the same code using Native-SQL works/
).IgnoreCase())
.List<myItem>();

}
}
}

See attached TestFixture.
As possible solution, Nhibernate could cut off text if it's longer as field defined in mapping.