It sounds like your download has been interrupted or corrupted in some way, I've downloaded and tested our recent stable build (4.4.1) and our current beta (5.0.1) and they both appear to be installing fine for me. If this continues to happen please let me know. We don't currently have an Alpha available but I assume you are using Forest Pack 5.0.1?
Thanks for reporting the vertical garden issue, if possible, could you send me a simplified scene file to email@example.com? It would really help to diagnose the problem.