I finally managed to reproduce the bug in a minimal example. The bug only occurs if I use a LinkButton to grab the content.

Here is my ASP.NET code:

<asp:LinkButton ID="Button1" runat="server" OnClick="Button1_Click" Text="LinkButton" />
        <asp:Literal ID="Literal1" runat="server"></asp:Literal>
        <ce:Editor ID="ceHovedinnhold" runat="server">
        </ce:Editor>

Codebehind:
protected void Button1_Click(object sender, EventArgs e)
    {
        Literal1.Text = ceHovedinnhold.XHTML;
    }

When i insert a table, and then click the linkbutton, the code in the literal has borders on the table:

<table style="border: 1px dashed #7f7c75;" border="0" cellpadding="2" cellspacing="2" width="500">

<tbody>

<tr>

<td style="border: 1px dashed #7f7c75;">&#160;</td>

        <td style="border: 1px dashed #7f7c75;">&#160;</td>

</tr>

</tbody>

</table>

If I use a Button instead of a linkbutton i get:

<table border="0" cellpadding="2" cellspacing="2" width="500">

<tbody>

<tr>

<td>&#160;</td>

<td>&#160;</td>

</tr>

<tr>

<td>&#160;</td>

        <td>&#160;</td>

</tr>

</tbody>

</table>