You can control the maximum file size allowed via the max_upload_file_size context parameter (added to Configuration.xml when running in the studio, or the application's context file when server-deployed). This parameter is set by default to ~50MB (50000000 bytes), so try setting a larger value.
Regarding the configuration changes you mentioned:
If you're still unable to solve please look in the logs (tersus.log and the tomcat logs), for more details on the error, and post them if you wish.
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