If you use redirected paths in Windows, e.g. for your user profile or app data, and they point to a network share, this can cause problems when running the AVD device emulator in Eclipse with the Android plugin.
By default, Eclipse always looks for the [virtual device].ini under c:usersusername.android, which is not always useful.
Some web sites mention a way of creating a symbolic link with mklink /J, but this is not possible with network UNC paths.
Set Windows system variable ANDROID_SDK_HOME, e.g. with value c:program files(86)androidandroid-sdk.
Restart eclipse and have a look at the AVD manager. It should now point to the new directory and you can create your virtual devices again.