I have used the core file manager code to create a file management PA.  When I click on refresh or occasional load of the page, the folder tree has nodes that are not responding to the cssClass and therefore cannot be selected.  No errors thrown.  Each refresh can change which nodes are affected.  Any number of nodes can be affected.
Any ideas?

Example is here: http://www.wrallp.com/images/issue.jpg

Two lines from view source are:

<n txt=Railroads key=0\RJM Engineering\MD 337\Data In\Railroads tTip=Railroads imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4242 />
<n txt=Storm_Drains key=0\RJM Engineering\MD 337\Data In\Storm_Drains tTip=Storm_Drains imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4245 />

Obviously there is no difference.

I changed the cssclasses to FMtreeNode etc for testing and am about to change back since this did not help the issue. 

I have noticed that the control Id Numbers seem to repeat:
<n txt=Hydrology key=0\RJM Engineering\MD 337\Data In\Hydrology tTip=Hydrology imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4242 /><n txt=Land_Use key=0\RJM Engineering\MD 337\Data In\Land_Use tTip=Land_Use imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4171 /><n txt=Municipal key=0\RJM Engineering\MD 337\Data In\Municipal tTip=Municipal imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4170 /><n txt=Railroads key=0\RJM Engineering\MD 337\Data In\Railroads tTip=Railroads imgIdx=0 js=nodeSelected(); css=FMTreeNode id=dnn_ctr1960_fileManager_DNNTree_4240_4123_4181_4180_4242 />

In this case "Railroads" cannot be selected.  A click on "Railroads" selects "Hydrology". 

I cannot seem to "view source" of tree in the 3.3.5DNN file manager to confirm behavior in 3.3.5DNN file manager.

The PA core was pulled from 3.1x version.
All fantastic coding and cheers to the authors.