Download the JNGP from wc3c and get the misc-data to get rid of any limitation. I'll search some links for you .. second.
E: Ok, got everything.
1.) At first, download the JNGP and the MiscData.txt (attached file).
» Jass NewGen Pack v5d
» MiscData.txt
2.) Create a folder named
UI in your Wc3-directory (example: X:\Program Files\Warcraft III\UI) and place the MiscData.txt in that folder.
If you want to take a look on the MiscData, just search for this text..
// Global height limits
// 0 = low ground, each cliff level = 128
MaxHeight=3000
MinHeight=-3000
.. you can change the MaxHeight/MinHeight for yourself but I think 3000 in each direction should fit.
The JNGP is easy to install, just unpack the data, and place it also in your Wc3-Folder .. just make a shortcut and start the editor.
Don't worry when you got a virus-alert .. that's ok. False alarm. (;
E: Excuse me? Him? eMo2LoVe is a girl. I can't dumb that down anymore.. what's the problem?
Download the stuff, place the miscdata in the created UI folder, unpack and start the JNGP. Et voilá.