servlet not responding

Hello,

With Jigsaw 2.2.2, I have two servlets. One deals with
a login window and the authentication process and the
other handles a file download subsequent to the login.

My problem is that after the file download dialog, if
I want to access again the link that opens the login
window, the servlet dispatcher is not responding (I
have an ugly HTTP 501/505 error). This behaviour
appears no matter if I choose Save or Cancel. I have
no idea of what's going on. If I reload the page with
the link, it works. 
How could I debug it? Anyone encountered this problem?

Many thanks,
Felicia

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