I have a DLink DIR-655 which was previously configured with WPA2 and AES under 802.11n. Unfortunately, the Droid X would lose connectivity after brief usage and wouldn't reconnect unless I stopped WIFI and reconnected. Other computers and laptops on the network continued to work so the problem is isolated to the Droid X.
I was able to resolve the problem by reconfiguring the DIR-655 with TKIP instead of AES. I thought I would post this in case anyone else ran into this problem. Hopefully Motorola/Verizon will fix this in the next firmware release.