Can't use ALTER TABLE in SQL Tab (phpmyAdmin)

[Silent Storm]

Hello.

This is pretty urgent, but I have created my tables in phpmyadmin, and when I go to edit them using this in the SQL tab:

"ALTER TABLE topics ADD FOREIGN KEY(topic_cat) REFERENCES categories(cat_id) ON DELETE CASCADE ON UPDATE CASCADE;"

This error comes up:

"#1005 - Can't create table (errno: 150)"

Clicking on details takes me to a page about InnoDB, but my tables have been set up to use that...

I have been stuck on this for a while and I don't know how to fix this.

Here is a picture of my tables.

http://i756.photobucket.com/albums/xx202/CrimsonEchoes/123_zps12e27cc8.png

Can someone please help me?

 

[Infopro]

This isn't actually an issue with your cPanel.

"ALTER TABLE topics ADD FOREIGN KEY(topic_cat) REFERENCES categories(cat_id) ON DELETE CASCADE ON UPDATE CASCADE;"

Interestingly enough, if you google the command just as you've posted it, you get lots of results with google.