How many pivot tables per sheet or workbook?

[StudioPhi]

EXCEL for Mac 2011 V 14.3.1
MAC OSX 10.7.5, 2.8 GHZ Intel Core i7

Good day everyone.
Running into a frustrating problem with pivot tables.
I am trying to create multiple pivot tables from the same dataset / workbook (file saved on LAN).
The pivot tables are created on different sheets, otherwise they will eventually overlap with the Table.
Once I have created 4-5 different pivots (on the same sheet) eventually I will get to the point where when I reopen the spreadsheet I get an error - all the pivot tables are lost and I am left with the data, but no pivots.

Is there a limit to how many pivot tables I am allowed per sheet / workbook?

Thank you for your help

Paul

[StudioPhi]

My colleague who is trying to access the same file from a wintel machine gets the following error message:

"Excel found unreadable content in FILENAME.xls. Do you want to recover the contents of this workbook? If you trust the source of this workbook click Yes"

And here is the log file of the error:

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
- <recoveryLog xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
<logFileName>error050000_01.xml</logFileName>
<summary>Errors were detected in file 'O:\FOLDER\SUBFOLDER\FILENAME.xls'</summary>
- <additionalInfo>
<info>PivotTable report 'PivotTable3' on '[Filename.xls]Analitico' was discarded due to integrity problems.</info>
</additionalInfo>
</recoveryLog>

Any help is truly appreciated!

P.