Anyone got any ideas on this? It has happened again for the user today, usually it is when they are adding links to the text or inserting a custom macro which puts an inline image in the text with some divs around it. However, today it happened when all they did was open a node and change one of the values in a multiple node picker field then click save.

This is the event log error that gets produced:

Event code: 4009
Event message: Viewstate verification failed. Reason: The viewstate supplied failed integrity check. 
Event time: 10/09/2015 12:30:43 
Event time (UTC): 10/09/2015 11:30:43 
Event ID: fbdb8f4d6c874238aa26a9e967f380ca 
Event sequence: 28439 
Event occurrence: 3 
Event detail code: 50203 

Application information: 
    Application domain: /LM/W3SVC/16/ROOT-1-130863402006589847 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: C:\Webpub\mywebsite.co.uk\www\ 
    Machine name: DED3045 

Process information: 
    Process ID: 52252 
    Process name: w3wp.exe 
    Account name: DED3045\ctAppPoolUser 

Request information: 
    Request URL: http://www.mywebsite.co.uk/umbraco/editContent.aspx?id=133631 
    Request path: /umbraco/editContent.aspx 
    User host address: 217.XX.XX.XX 
    User: [email protected] 
    Is authenticated: True 
    Authentication Type: Forms 
    Thread account name: DED3045\ctAppPoolUser 

ViewStateException information: 
    Exception message: Invalid viewstate. 
    Client IP: 217.XX.XX.XX 
    Port: 38277 
    User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.85 Safari/537.36 
    PersistedState: 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 
    Referer: http://www.mywebsite.co.uk/umbraco/editContent.aspx?id=133631 
    Path: /umbraco/editContent.aspx 

Custom event details: 

Hey there, did you every resolve this, having the same issue on one of my sites

No unfortunately not, I started looking at upgrading to Umbraco 7 to see if that would resolve the issue but this is a very big and heavily customised Umbraco site so it required a lot of testing and the customer asked us to put the upgrade on hold for the time being to work on other projects (they said they would live with it for the time being).

I haven't heard them mention it lately but then that is probably because they know we were planning to test the upgrade option which they have asked us to stop for now.

Please let me know if you do find a solution because I don't want to upgrade to 7 if I don't have to, especially as it may not even resolve this problem.

There's a related error on the Umbraco issues site which makes me think it has not been resolved in Umbraco 7 (http://issues.umbraco.org/issue/U4-6900) so would not undertake an upgrade just to solve this, especially if it is complicated.

I've followed all the advice on the linked page from the error (and some others) - nothing has solved it, which leaves me with a very grumpy client, because they keep losing content they are adding.

Will let you know if I find anything

That error is similar although the issue our user was experiencing was not due to a timeout, they would open a node and be editing it then click "Save" (not Save and Publish) and they would get the error. It seemed very random and I even added javascript onto the page the backend of Umbraco to capture what was in the text-editor at the time but could not find anything to point to what could be causing the issue.

Hi! I have the same error, someone found the solution?

I haven't yet, I did start testing an upgrade to Umbraco 7 (to see if this resolved the issue) but this is a very large site with a lot of customisations and the customer told us to hold off for the time being due to other more important projects.

We haven't yet got back around to looking into this and the customer is just living with the issue for the time being so I would be very interested if someone does find a solution or they can confirm it is in fact fixed in Umbraco 7.

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