On RAD 8.5 the install routine fetches com.lowagie.itext_1.5.4.v20090305.jar.pack.gz from a mirror.

On RAD 8.5 the install routine fetches 
com.lowagie.itext_1.5.4.v20090305.jar.pack.gz from a mirror.  It then decides 
it doesn't like what it downloaded and gets the same file from a different 
mirror.  It decides it doesn't like the file and repeats the process with a 

different mirror.  It keeps doing this forever. 

Solution :  Apparently one of RAD's repositories is messed up.  
Don't use RAD's default repositories.
First, add the desired Eclipse update site URL to RAD.  In the "Install New 
Software" dialog click on the Add button.  For Name call it whatever you 
want, I chose "Subclipse Direct 1.10.x".  In the location field paste the 
appropriate Eclipse update site URL from the subclipse.tigris.org Download 
and Install page.  Click OK.
Second, in the Work With drop down select the site you just added.
Third, you should see Subclipse and SVNKit below.  Expand them and install 
the projects/features you want.
Fourth, uncheck the "Contact all update sites during install to find 
required software" checkbox.  Doing this step without doing the first 3 
steps will NOT work.  
Fifth, continue the install process as normal.  It won't hang up on itext 
anymore.