He have the dhtmlxTree_v12_Pro_51102.
The grid give us a javascript error on horizontal scroll.
The error is “ev has no properties” in _doContClick method. I added the code if (!ev) return true; and it works. Can you check this?
In latest version of code - _doContClick called only from event handlers and it must receive event object, so in theory it must work correctly in all situations.
Can it be possible, that you are using some custom code which triggers onmousedown or oncontextmenu event for dhtmlxgrid ?
If you have any kind of sample where problem can be reconstructed - please provide such sample ( you can send it directly to support@dhtmlx.com ), because it works correctly in local samples.