Invalid Viewstate - Request path: /ScriptResource.axd

Getting these errors in our logs more and more, they have been building up recently. Thirty today was the final straw, I had to investigate more.
The exception is as follows:

Process information: 
    Process ID: 5164 
    Process name: w3wp.exe 
Exception information: 
    Exception type: HttpException 
    Exception message: Invalid viewstate. 
Request information: 
    Request URL:>span>li><li><span><a</a>span>li><li><span><a</a>span>li><li><span><a</a>span>li><li><span><a%20href=href=href=href= 
    Request path: /ScriptResource.axd 

I found a promising lead from Project 31-A blog that lead me to Microsoft connect and this report, Bug IE8 – 4K dropped - "Invalid viewstate" when loading ScriptResource.axd or WebResource.axd (asp net)
It seems there is an IE8 bug that might explain the occurrences growing. The description of the issue matches what we are seeing to a tee. I have started work on trying to mitigate our exposure to the issue by removing the META-Content tags content="text/html; charset=ISO-8859-1" from our pages that have them and hope this reduces the impact.

I am worried that this IS affecting the user experience of our site. More testing required on this one…