I agree with Cody21. We will need some additional details in order to help you out. I want you to be able to take full advantage of this wonderful device.
Are you trying to install applications from the Market to the Droid X? http://support.verizonwireless.com/clc/devices/index.html?p=5369&m=
If so, what happens? Any errors?
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If this was a once or twice occurence, I've noticed some strange behavior with the Market lately.
I tried to download an app and received an Error Message in the Notification Bar. It was real quick and wasn't in my Notification list when I pulled it down (like a missed call is).
I did see it said something like "Not Enough Memory".
I rebooted my phone and and tried it again and the download was successful.
I noticed the same thing during an automatic update of an app. This time, I tried it again manually and it was successful.