I know it is a bit late, but in case anyone comes here via search - here is a solution to set hover style for rows using MouseOver / Out CSOM client-events, hopefully it will be useful:

I made something way sampler then your way, and it works every time.

First off set your selectedRowStyleDefault with the style you want it to appear.

After, set your mouseOver and mouseOut event handlers like you did (on 2 javascript functions).

Then in your javascript functions use this code: 

function Over(tableName, itemName, type) {  

if (type == 0) { // Are we over a cell

var row = igtbl_getRowById(itemName);

row.setSelected(true);

}

}

function Out(tableName, itemName, type)}

if (type == 0) { // Are we over a cell

var row = igtbl_getRowById(itemName);

var grid= igtbl_getGridById(row.gridId); // Get the grid

var rowActive = grid.getActiveRow(); // Get the current active row

if (rowActive != null ) {

// We verify if there is a selection made by click, if there is, we let it selected

if (rowActive.Id != row.Id)

row.setSelected(false);

}

else

row.setSelected(false);

}

}

And this will light up any rows over!

This helped me quite a bit.  I needed this very thing. 

I added some 'null' checks to handle the row header problem.

Thanks!

 This bombs when you hover over a header row.  Any ideas on how to fix this problem?