archalien,
From this link http://techpubs.borland.com/together/2008R2/EN/readme.html
It lists the update site as : http://altd.borland.com/update/eclipse3.5
Can you try installing the plugin using http://altd.borland.com/update/eclipse3.5 ?
Here are the steps :
1) Uninstall the plugin from the MyEclipse Configuration Center.
2) Restart the IDE and check if you are able to open the Enterprise Perspective without any issues.
3) If there are issues, Reinstall the MyEclipse from Pulse.
Please follow below mentioned steps to reinstall ME-
a. Open pulse. If you don’t have pulse, you can download the same from http://www.poweredbypulse.com
b. Login to pulse. You can also login anonymously.
c. This will redirect you to the pulse-explorer. From the top left hand corner dropdown, select the realm – “Eclipse – Galileo”
d. Choose “MyEclipse 8.6” from “My Profiles”.
e. Right click on MyEclipse 8.6 and from the context menu click on [Re-install and run]
4) Now try to install the plugin using the update site : http://altd.borland.com/update/eclipse3.5
Let me know how it works for you.