Hi NFL1,
Could you tell me which version of office are you using, 32bit or 64bit? You said this issue always happened when open attachments from outlook and files in C-Driver.
For opening attachments from outlook, it might there is a conflict between the preview pane and Excel. You can try to hide the preview pane as a workaround to solve this issue. Please refer to this link:
https://support.microsoft.com/en-us/kb/2526883
It is often the case, if your file is large or contains a large amount of features, it is possible you are running low on available memory resources. If you work with extremely large data sets, the 64-bit version of Office may perform better for you. 32-bit
office you run are limited to making use of only 2GB of RAM. And this is one of the reasons occur the issue, you can via these links to get more information about this issue and detailed methods to solve this problem.
https://support.microsoft.com/en-us/kb/2779852
http://blogs.technet.com/b/the_microsoft_excel_support_team_blog/archive/2012/05/22/quot-excel-cannot-complete-this-task-with-available-resources-quot-after-installing-ms12-030.aspx
Please try these methods and let me know if they work, I am glad to help and forward to your reply.
Regards,