Index out of range error exporting to Excel

i've noticed that others have gotten this same error, when trying to
export to excel they get the following error, it seems it hasn't been
something dealt with, maybe because microsoft cannot reproduce it
Exception of type
Microsoft.ReportingServices.ReportRendering.ReportRenderingException
was thrown. (rrRenderingError) Get Online Help
Exception of type
Microsoft.ReportingServices.ReportRendering.ReportRenderingException
was thrown.
Index was out of range. Must be non-negative and less than the size of
the collection. Parameter name: index
I am using SP2 and this error is happening both in the report designer
as well as in reporting services itself.
my situation.. i have a report.. with grouped data, inside the footer
of one of the groups i put a table, then in that nested table i have a
group, and in the group footer of that i have a line with the field i
am grouping on as well as a sum.. at first i thought maybe it had to do
with something that i hide the detail, and group header of the nested
table, but i showed that it it still failed..
one thing that made it work, was when i moved this nested table out of
the group footer of the parent table, and into the footer of the nested
table, when i did that the error no longer happened (however i need to
be able to have it in this group)..
if you need some examples maybe i can adapt my report (take out our
business specific info) and send it on to you.
Karl
the error only happens when exporting to excel..correction below:
one thing that made it work, was when i moved this nested table out of
the group footer IN THE PARENT TABLE of the parent table, and into the
footer of the PARENT
table, when i did that the error no longer happened (however i need to
be able to have it in this group)..