R help - May 2010 - A problem importing a particular date from SQL Server

Hello,

I'm importing a table from a database in SQL Server using the RODBC package
(function sqlQuery()).  But I've encountered a problem and I can't
figure
out the cause: in all records with date 1988-12-01 (yyyy-mm-dd) I receive an
NA in R (when the date is OK in the SQL database).

I tried changing the date to 1988-12-01, and it worked fine, but I can't
find the reason for transforming the first of december in NA, has anyone
found this before?  Is there any reason for this?  And should I check the
rest of the dates to see what happened (I took a sample and the rest were
OK)?

I forgot, that field in the database has "datetime" format.

Thanks,
Carolina.