Marcos -
The exact same thing happens when you create a treeview that has many, MANY nodes - it takes forever to build the structure. Once the structure has been created, it will be painted.
One answer is to find a folder with fewer sub-folders, then code your way to the correct folder if the parent folder is the one you want.
In my own code, I've implemented a LIMIT on the treeview creation that stops at a set number, then display a query to the user: "1500 rows have been retrieved. Continue retrieving data? Y/N". If the user says NO then I paint the treeview. You might be able to do something like that.
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I definitely think that some kind of LIMIT parameter needs to be on any object that gets, reads, or builds something that is required to wait on fun-units;i.e. sub-nodes or dub-folders. JMHO.
Olan