console error "Cannot read property mData of undefined"..??

These can be the possible issues related to this error :

1.Table must contain <thead> and <tbody> tags, otherwise it throws this error, for example below table will throw error

<table id="erroTable">
    <tr>
        <th>Test</th>
        <th>Test2</th>
    </tr>
    <tr>
        <td>Data-1</td>
        <td>Data-2</td>
    </tr>
</table>

<!--Error may occur because of no tbody and thead defined-->

2. Mismatched number of columns(this table will also throw error) :

<table id="ErrorTable">
    <thead>
        <tr>
            <th>Test</th>
            <th>Test2</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>Ok-1</td>
            <td>ok-2</td>
            <td>Error because of this extra value</td>
        </tr>
    </tbody>
</table>

3.It can also occur if you have table arguments for 'aoColumns':[..] which don't match the correct number of columns, means may be you have defined aoColumns for 4 columns but there are only 2 columns in table.

4.Could occur due to Duplication of table Id(two table with same Ids)

Most of the times, this error occurs when number of columns in <thead> <th> is different than <tbody> <tr> <td>

But it can also occur if number of columns in 'aoColumns':[ ] does not have the correct number of columns.

For example, this configuration will not work

<table id="datatable">
    <thead>
        <tr>
            <th>col 1</th>
            <th>col 2</th>
        </tr>
    </thead>
    <tbody>
        <td>data 1</td>
        <td>data 2</td>
    </tbody>
</table>
<script>
        var datTable = $('#datatable');
        datTable.DataTable({
            'order': [[ 1, 'desc' ]],
            'aoColumns': [
                null,
                null, 
                null,
                null,
                {
                    'bSortable': false
                }
            ]
        });
</script>

But this will work:

<table id="datatable">
    <thead>
        <tr>
            <th>col 1</th>
            <th>col 2</th>
        </tr>
    </thead>
    <tbody>
        <td>data 1</td>
        <td>data 2</td>
    </tbody>
</table>
<script>
        var datTable = $('#datatable');
        datTable.DataTable({
            'order': [[ 1, 'desc' ]],
            'aoColumns': [
                null,
                {
                    'bSortable': false
                }
            ]
        });
</script>

Hope this helps.