Tried to create an AVD from the eclipse environment in the following steps:
Looks like this is a bug reported since ADT 22.6. Please find more information in this post:
Cannot create or edit Android Virtual Devices (AVD) from Eclipse, ADT 22.6
I was actually able to reproduce the same issue inside of my environment. As a workaround I was able to open the AVD manager outside of Eclipse by using the following command in terminal:
android-sdk-location/tools/android avd
After opening the AVD manager outside of eclipse it let me create the device successfully. Please note you will have to restart Eclipse once you create the device in order for it to show up in the list of usable devices.
Please look at this similar post for some more suggestions if needed:
AVD Manager - Cannot Create Android Virtual Device
EDIT: Update to latest AVD manager and this issue should go away