The following procedure causes high CPU load and that OpenOffice.org stops
responding. I have to killall soffice.bin to end it.

1. Open a new spreadsheet window
2. Select a cell (B4) with the mouse
3. From menu select Window|Freeze
4. Select a whole row below the freeze-line by clicking on the row number [row 6]
5. From menu select Data|Outline|Group
6. Scroll down [by one row or more] [by klicking on the bottom scroll arrow]
7. Again select the row that was "grouped" before (row 6) if not already selected
8. From menu select Data|Outline|Ungroup
9. Scroll down or up [by klicking on the bottom or top scroll arrow]

And variations of the procedure:
3. From menu select Window|Split
(then the scrolling is to be done in the part of the window where are the
grouped rows/columns)

Another variation:
4. Select a whole column to the right of the freeze/split-line by clicking on
the column letter [column D]
5. From menu select Data|Outline|Group
6. Scroll to the right [by one column or more] [by klicking on the right-hand
scroll arrow]
7. Again select the column that was "grouped" before [column D] if not already
selected
8. From menu select Data|Outline|Ungroup
9. Scroll to the left or to the right [by klicking on a scroll arrow]

No problem when group/ungroup on rows/columns above or to the left of the
freeze/split line.

As far as I can tell the bug appeared in 1.1beta2 (for Linux); 1.1beta1 was OK.
Windows version 1.1.x is also affected, though I did not get a chance to check
the exact version. Version 1.0.2 is not affected.