I'm getting this error when trying to install, and it's not letting me click on the next button because of the script error, whether I select yes or no on this screen. I know it's not an issue with the installer itself, maybe something else needs updating?
http://i43.tinypic.com/i2rt09.png

//edit: oops going through the random questions thread (should've done that first) and there's a solution there that I'll try

it worked and incase anyone else needs:

IF YOU ARE HAVING SCRIPT ERRORS !

This thread is just to help anyone who's having trouble getting past the license agreement because of script error.

{{{Also if you've found this thread has helped please reply saying it worked so it gets bumped to the front page of the forums since a lot of people were having this issue}}}

1. Find and open your FFIV beta folder/ or you can just go to start and type in beta and you should see the "FFIV" beta file there .
2.Open FFIV_BOOT w/notepad (if notepad is not working try another program like wordpad or something).
3.There should be a "0" next to EulaAgreement, erase that "0" and put "1" in its place, then go to file and save then close out. After you have saved and closed out relaunch.
4.Also if you are using windows 7 make sure it's up to date INCLUDING IE.
5. If all else fails ( SE says: ) right click the beta app on your desktop and run as administrator. ( I didn't do this step because the previous steps solved the issue for me which is why its the last step )

Doing all of these from step 1-5 should eliminate this script error and allow you to continue with the DL process.