Filtering in a radgrid and Filemanager in radeditor doesn't work anymore

[develop about:blank]

Greetings,

I got 2 problems with my telerik controls. the first one is that filtering doesn't work in my radgrids. I'm using several radgrids on my websites on different page under the same masterpage this is the error I get when i try to filter:

The other problem i have is that the filemanger function in my radeditor doesn't work.
I have added:

<add path="Telerik.Web.UI.DialogHandler.aspx" verb="*" type="Telerik.Web.UI.DialogHandler" validate="false" />

to the web.config and i defined the filepaths as you can see below:

<telerik:RadEditor ID="txtWhoAreWe" ShowSubmitCancelButtons="false"
        runat="server" AllowCustomColors="true">
        <ImageManager ViewPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" UploadPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old"
            DeletePaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" />
        <MediaManager ViewPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" UploadPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old"
            DeletePaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" />
        <FlashManager ViewPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" UploadPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old"
            DeletePaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" />
        <TemplateManager ViewPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" UploadPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old"
            DeletePaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" />
        <DocumentManager ViewPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" UploadPaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old"
            DeletePaths="~/_upload/RadFiles/New,~/_upload/RadFiles/Old" />
    </telerik:RadEditor>

Yet the filemanager doesn't work whenn i open one of the filemanager all buttons are are disabled and all i can do is close it.

I hope you can help me.

[develop about:blank]

Here is the screenshot of the error i get whenn i try to filter

[Fiko]

Hi,

I was unable to reproduce the problem on my side. Could you please open a new support ticket and send me the code-behind files as well? The error that you experience is a server-side generated error and most probably it comes from one of the codebehind files.

Best wishes,
Fiko
the Telerik team

[develop about:blank]

Oke fixed it,

i removed the following line from the web.config:

<xhtmlConformance mode="Legacy"/>

And now it working like it should.