We are using OOo in German on Windows 2000 and on Linux and have the following
problem with charts:

Charts with data from more than one spreadsheet table don't organize the data
properly, resulting in incomplete/inaccurate charts.

The error can be shown as follows:

Make one Table with three rows.  Make the first row ten columns wide, and put
the number from one to ten in them.  Make a second row as wide as the first with
the numbers from one to ten. In the third row, put the numbers from 11 to 20.

Make a second table with one row ten columns wide.  Put the numbers from 11 to
20 in the cells.

Now make a line diagram using the three rows from first table.  Select "use
first row for labels" when entering the data range.  This will make a line chart
with two lines, ten data points long.

Make a line diagram using the first two rows from the first table and the single
row from the second table.  Use the same settings as for the first diagram. 
This line diagram will have one line containing ten data points on a diagram
wide enough for twenty points.  The data from the second table won't be shown.

This problem was found while trying to import complex spreadsheets from Excel,
and was found to be a problem with the way OOo handles charts with data from
multiple tables.  The spreadsheets involved take measured data from a sewage
plant water treatment system, and do long, complex calculations on them.  At the
end, the data needs to be presented with the final results from several tables
combined into one diagram to summarize the efficieny of the plant.  It is not
practical to combine the tables involved into one table - the result would be
too complex and overloaded.

The problem is not related to the Excel import, as it can be duplicated using
native spreadsheets from OOo.

I would suggest a complete review of the way OOo handles charts using data from
multiple tables, and perhaps of the whole chart data entry system - it seems to
have some serious drawbacks as others have mentioned.

I will post a spreadsheet as an example.