Dynamically updating tablesorter? Two problems

Dynamically updating tablesorter? Two problems

I have an empty table and I use tablesorter:

$("#hourly-table").tablesorter();

Works beautifully. Every 30s I delete the contents of the table and add new rows. I then do:

$("#hourly-table").trigger("update");

it *seems* to work except for two problems:

1) Clicking a sort title correctly sorts the rows, but the odd/even zebra striping is wrong and is only fixed when the update is triggered
2) Tablesorter seems to be caching the rows I delete. They don't re-appear but after a short period of time the browser (Firefox 3.6 on Linux) becomes really, really sluggish.

Is anyone using tablesorter with a dynamic table? I will look at other table plugins, but tablesorter is better for me (apart from the problems!) because it is lightweight in terms of features I don't need and it displays the 20 columns I have.

Thanks