The column names in the T-SQL statements that Limesurvey is generating are not wrapped in []. My guess is that this is causing MSSQL server some confusion; the "AND 624695X14X235 = @P1" portion of the statement may be ambiguous. (It may be trying to perform a comparison of "624695X14X235" itself as a value instead of performing the evaluation on the values in the 624695X14X235 column?)

It appears that wrapping [] around the column names solves this issue.

Test:

Isolating the Select statement and running it by itself in SSMS (SQL Server Management Studio) and replaceing @p1 with the 'Y' value supplied from the form, this statement causes an error:

SELECT COUNT(*) FROM [dbo].[survey_624695] [t] WHERE (submitdate IS NOT NULL) AND (624695X14X235 = 'Y')

Result: Error: Msg 102, Level 15, State 1, Line 1
Incorrect syntax near 'X14X235'.

After wrapping 624695X14X235 in brackets, the statement runs successfully:

SELECT COUNT(*) FROM [dbo].[survey_624695] [t] WHERE (submitdate IS NOT NULL) AND ([624695X14X235] = 'Y')

Result: Returns a correct count value.

(Note: the column 624695X14X235 in the table [dbo].[survey_624695] in the Limesurvey database is a varchar(1) field.)