Hi, When i upgraded my old version of Limewire PRO to the new version, i opened it and it said ' Your save folder is not valid. I may have been deleted, you may not have permissions to write on it, or there may be another problem. Please choose a different folder.'

I chose a different folder and it says the same thing! I am really stuck and need some help. I havn't found anything anywhere else to help me so i was wondering, can someone help me!!!!

Thanks.

Try deleting LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used older versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire
This will kill all of your settings within options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
LimeWire Pref Folder in Vista

Once you've deleted that prefs folder, the location for saving will revert back to default. If you want to change the location for saving, hopefully it will work now!