Hello Peter,
Please go to
http://bugs.mysql.com and file a bug report for each problem you have encountered using MySQL for Excel and attaching clear steps to consistently reproduce the problem, and any additional information about versions used, environment and data.
This is the best way we can improve the product.
Are you positive you can consistently reproduce the problems you are describing?
For example the "Out of memory" error can be consistently reproduced on your end?
The product is stable enough for production environments, some of the problems you are seeing may be specific to your environment, but if you think they are general and reproduced consistently, filing bug reports is the best way to get them fixed.
Thanks for your feedback and your support.
Best regards.
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Javier Treviño
MySQL on Windows Team