To edit an existing link, place the cursor anywhere in the link and click Edit > Hyperlink. The Hyperlink dialog opens. Make your changes and click Apply. If you need to edit several hyperlinks, you can leave the Hyperlink dialog open until you have edited all of them. Be sure to click Apply after each one. When you are finished, click Close.
The standard (default) behavior for activating hyperlinks in OOo 3 is to use Ctrl+click. This behavior can be changed in Tools > Options > OpenOffice.org > Security > Options, by deselecting the option Ctrl+click required to follow hyperlinks. If clicking in your links activates them, check that page to see if the option has been deselected.