All data disappaers from report when fourth data table is added?!

I've designed a report in CR XI that relies on a stored proc and two additional linked sql tables. Everything works great in this configuration.

BUT, when I add one more data table (a fourth data source), no data appears in the report. The link between this newest table and the other tables is a good join: I've verified it in sql, in Access, etc...

I even attempted to "work around" the problem by adding a subreport that is based on the new sql table, instead of including the sql table to the main report. Unfortunately, the subreport approach yields the same problem of no data displaying in the report.

Is there some sort of limitation on how may data sources can be used in a CR report if one of the sources is a stored procedure??!

Thanks in advance for any assistance with this problem,

--Pete