Resolution
To correct this problem locate the versaSRS database table 'tbl_FileTypes' using SQL Server Enterprise Manager or SQL Server Management Studio Express or equivalent.
You will the need to add a new record for .DOCX &/or .XLSX files as follows:
FileExtension: DOCX
MimeType: application/vnd.openxmlformats-officedocument.wordprocessingml.document
SendAsAttachment: True (MS SQL 2005 / 2008) or 1 (MS SQL 200)
You can also add an entry for XLSX files (MS Excel 2007) as follows:
FileExtension: XLSX
MimeType: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
SendAsAttachment: True (MS SQL 2005 / 2008) or 1 (MS SQL 200)
Note: if you upgraded from an earlier version of versaSRS you may need to increase the character length of the field MimeType.
As of versaSRS 4.0, the MimeType field should be set to a Data Type of nvarchar(250).