I freshly installed OOo 641c after using SO 5.2 for almost one year without a
* similar problem:
* 
* A have a simple spreadsheet which I originally created in MS Excel. I
* modified the file the file several times in SO5.2 without any problem. Now,
* when I used OOo, the file size increased from about 800 kB to over 5.2 MB.
* 
* The only thing I did is I inserted and deleted some cells.
* 
* Now I found, that when I create a new file and copy the entire spreadsheet
* content to the new file, the size is also 5.2.MB.
* But If I only copy colums A to C, the size is 800 kB again. So there must be
* something in the colums D to IV which make the file that big. If I delete the
* rows D to IV, the size is also reduced to 800kB.
* 
* I checked the big file with MS Excel: No problem to open, but stays big if I
* do a save as. But reduces the size if treated as above.
* 
* The file stored in the OOo xml format is only 150 kB.
* 
* I use an old P 133, 64MB RAM, W95b
* 
* For reference, I attach the zipped version of the file.
* 
* Would be great if somebody has an idea.
* 
* Regards, Stefan