Our guess is that the error you report is related to page caching problems.
We implemented improvements in this area recenlty. They will be included in the coming release of Sitefinity v. 3.5 within two weeks.
Our recommendation to would be to upgrade to Sitefinity 3.5.We have all reasons to believe that this will solve your problem.
Please, inform us if that is not the case.
the Telerik team
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