Just to let you know, I did some testing with jQuery 1.4.

I did a test with jqGrid 3.6.2 and jQuery 1.4a1 and a2.

With 1.4a1 it looks like everything is working for me (treegrid, custom formatters, custom buttons), but with 1.4a2 my custom button doesn't show up.

Apparently there is a problem of “too much recursion” in 1.4a2, that's a known issue and bug for the jQuery Team.

So this seems like good news for jqGrid.

Stefan