So I have been having some problems installing APEX over the past few days. In addition to a unstable computer, the install was failing to correctly work out. The symptoms were that I could not import an application into APEX 3.0, and some of the ICONs were not showing on screen (the red x just appeared). So, after going over and over the application guide only to no avail, someone ( http://dgielis.blogspot.com/ ) gave me a link to some important information....I used this data on my first desktop install, but forgot about it on my subsequent laptop installation. After using these directions, all turned out perfectly. Here are the directions and a link to the page:

If you have reviewed the differences described above and want to proceed to install Application Express 3.0.1 in your Oracle Database XE, first follow step 3.2 of the Application Express Installation Guide. The command and arguments used to install APEX 3.0.1 via SQL*Plus should be: @apexins password SYSAUX SYSAUX TEMP /i/
Once you complete the standard install, you need to perform the following steps to complete the upgrade:
Connect to SQL*Plus as SYS
@APEX_HOME/apex/apxldimg.sql APEX_HOME
@APEX_HOME/apex/apxxepwd.sql password(where password is the password of the Application Express internal ADMIN account) For the steps above, APEX_HOME is the directory where the Application Express software was unzipped.

http://www.oracle.com/technology/products/database/application_express/html/3.0.1_and_xe.html

So, now that everything is installed fine, and I feel well practiced in conducting installs, on to application development.