Improve behavior in case of error in transmission

[GoogleCodeExporter]

Sometimes, during import, some errors occur leading to messages such as:
Unexpected size in header for getSessionsDetails (step 3): 1484 != 1424 - 4

In such cases, the output is corrupted and meaningless.

The best way to handle this would be to find out how to ask for retransmission 
of the same data. However, a possible workaround is to reimport the whole 
session.

Original issue reported on code.google.com by [email protected] on 27 Sep 2013 at 9:58