OR qualifiers

Hi everyone. I'm having a problem with a JDBC connection to a FileMaker database. In a nutshell, I have a table with about 300,000 records in it, that I am using for large data set testing. Searches/queries to this data are very snappy, both from FileMaker and JDBC, except for when I do something like this:

SELECT t0.Column1, t0.Column2, t0.Column3 FROM Table t0 WHERE (t0. Column1 = 200000016 OR t0. Column1 = 200000029)

Note that Column1 is indexed, and searches on it from the FileMaker GUI are very fast. Additionally, this query runs as quickly as I would expect it to when only searching t0.Column1 = X, but WITHOUT the second qualifier. However, as soon as I add a second search criteria to pull up more than one record, the query slows dramatically, taking minutes to complete instead of seconds.

So, can someone think of something else that might be causing this problem, or what I can do to debug it? Or can FileMaker's JDBC driver *actually* not handle an OR with large data sets?