Error 502 in OpenOfficeSpreadsheet formula

"Using OpenOfficedotorg 3.1.1 with the following data:

Start End Elapsed
12:30:00 PM 05:30:00 PM 05:00:00
08:30:00 AM 05:30:00 PM 09:00:00
08:30:00 AM 08:00:00 AM 00:00:00

I used the following formula for the Elapsed column:

=IF(B2 < A2; 0; B2-A2)

Start and End use the formatting:

HH:MM:SS

And for the Elapsed column, I used

[HH]:MM

This seems to give the results you want."