SSAS MDX EXCEL: Memory error: While attempting to store a string, a string was found that was larger than the page size selected. The operation cannot be completed.

Adding ";Optimize Response=3" to your connection is one viable workaround.

The original solution is posted here: https://connect.microsoft.com/SQLServer/feedback/details/779232/excel-pivottable-error-while-attempting-to-store-a-string-a-string-was-found-that-was-larger-than-the-page-size-selected

Seems the problem is caused by the OleDB driver. Adding this to SSMS connection string as an additional parameter did not fix the issue.

Another work around is to issue the MDX statement using SQL and a linked server.