Event Groups using ReadOldPDP

[alkim@cattell.psych.upenn.edu (Albert E Kim)]

When I use ReadOldPDP to read an environment containing event groups 
marked by "# startgroup" and "# endgroup", I get the error "OldPDP
type events file contains an endgroup directive without a matching
subgroup!"  I am positive that my endgroup and startgroup commands are
matched one for one.   An example of my input is this:

# startgroup
Foo_0_A_P_0_2   1       0       0       0       0       0
        1       0       0       0       1       0
Foo_0_P_T_2_2   0       0       0       0       0       1
        1       0       0       1       0       0
Foo_0_T_T_2_2   0       1       0       0       0       0
        1       0       0       1       0       0
# endgroup

Does anyone know what could be going wrong here?
Thanks for any help,
Al Kim
alkim@psych.upenn.edu