Error in mscorlib (invalid length for a base-64 char array.)

[Guest]

Hi there

I have spent some time browsing for a solution to the following error but
have unfortunatly not found any solution yet (the deleted parantheses means
that i have removed the information before posting here):

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WWW Host
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Host: (deleted)
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MESSAGE
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MESSAGE: Invalid length for a Base-64 char array.
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SOURCE
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SOURCE: mscorlib
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QUERYSTRING
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QUERYSTRING:
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TARGETSITE
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TARGETSITE: FromBase64String
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STACKTRACE
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STACKTRACE: at System.Convert.FromBase64String(String s)
at System.Web.UI.LosFormatter.Deserialize(String input)
at System.Web.UI.Page.LoadPageStateFromPersistenceMedium()

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User Cookie values
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(deleted) = language=1
ASPSESSIONIDSSDBTCST = NCLPHPPAPAHBKLNPDIIGNFGB ASP.NET_SessionId =
dp5hlk22xugsu055wwu4azut konfiguration =
authenticated=jeps&brugerid=3559&uid=3559&kursistnavn=jytte&brugernavn=kmd1&forumid=-1&kursist_efternavn=(deleted)&udbyder_id=1&underviser=False&mail=jgd@(deleted).dk&courseid=1431&admin=False
..ASPXAUTH =
17600CD11D0845D48BF012E091F0B6AB791D64A8B4666AB27984425C8DB7471371844007B9B2000BADDEF169A83BC4F6B219D6B59F99896BB384D8CD1BE5812D

This error occurs on our website for some of our users, not for alle but for
someting like one out of five hundred.

Our server is a windows2003 server standard edition (sp1) running as a
virtual server in a Wm ware enviroment. It is running the .Net framework in
version 1.1.4322.573

I suspect that it is some sort of proxy server at the clients that messes up
the viewstate but i dont know for sure?




Any Ideas how to start resolving this issue?

 

[Scott Allen]

This error occurs on our website for some of our users, not for alle but for
someting like one out of five hundred.

Do you actually have the bug report from a user or are you seeing this
error because you log all exceptions? I've seen this error occur when
someone has written a web crawler or other spider type program that
tries to post back to a form but doesn't encode the viewstate hidden
parameter correctly. My first step would be to check the user agent
string in the IIS logs for the request and see if request was made
from an actual user or a bot.

 

[Guest]

Hi Scott

Do you actually have the bug report from a user or are you seeing this
error because you log all exceptions?

Thank you for taking time to answer my posting.
Yes I have cheked that this error occurs from real users. Some of the
information in the cookie is first written when the user is authenticated.