P: (Windows) Panel is limited to 1600 items (folders, keywords, etc)

Lightroom bug - hit a folder limit and unable to select the newly imported folder.452497 photographs across many drives in one catalog.The S drive has 214341 photos. It's the largest drive and so had many more folders than the previous drives.S:\Master Photos\ contains ~1633 folders. I know that's a lot but that is how her filing system was started. Those are the sequential numbers from 2220 - 3853 but there may be a sub folder or two or deleted folder in there so that's why the number is ~ approximate.Folders are labeled "sequential number"-"date" so 3853-20150316Adding one more folder caused Lightroom 4 to not allow the last folder to be clicked on and not show any images. The T:\ drive (offline, collapsed and below the S:\ drive) was collapsed and the label was overlaid on top of the "Collections" section label. Updated to latest version of Lightroom 5 via her new cloud account, had it rebuild the catalog and the same problem occurred.Created a sub folder S:\Master Photos\2012 and moved 15 of the folders into that folder. The 2012 folder was expanded so the list was actually one row larger and the last good folder wouldn't open. I collapsed the 2012 folder and now all the bottom folders were accessible.It appears there is an object limitation or a fixed array or something that is causing the folder list to become finite. She said a similar thing happens on her keyword list until she collapses some of the groups but I didn't check that out.