To reproduce this problem :

• have an assignment in which you can upload several files
• add a submission with several files; these have to be large enough (a few megs)
• click on "Export to portfolio"
• select "Wait"
• you should get these errors :

Failed to start communication with remote server: remote server error: code: , message: Failed to retrieve zipfile from remote server: An error occurred at the remote server. Code: 500ERROR 4:
4: remote server error: code: , message: Failed to retrieve zipfile from remote server: An error occurred at the remote server. Code: 500

Debug info:
Error code: failedtoping
Stack trace:

line 212 of /portfolio/mahara/lib.php: portfolio_export_exception thrown
line 510 of /lib/portfolio/exporter.php: call to portfolio_plugin_mahara->send_package()
line 227 of /lib/portfolio/exporter.php: call to portfolio_exporter->process_stage_send()
line 233 of /lib/portfolio/exporter.php: call to portfolio_exporter->process_stage()
line 233 of /lib/portfolio/exporter.php: call to portfolio_exporter->process_stage()
line 265 of /portfolio/add.php: call to portfolio_exporter->process_stage()