Verizon LTE services nationwide remain out, more than 24 hours after they first went offline. The company verified the outage on its Twitter account. The service first went offline on Tuesday night.
In addition, Verizon has previously said that LTE devices would switch to CDMA mode if they were in an area with no LTE coverage. In this case, HTC Thunderbolt users (the only handhelds currently on Verizon's network supporting LTE) are seeing 1X mode, not 3G, Verizon has admitted in a later Tweet.
Voice on Thunderbolts is apparently working fine, but that should be no surprise. Verizon's current LTE implementation uses CDMA for voice, though that should change in 2012.
Verizon's LTE network is nascent, and thus an issue like this should not be unexpected. The 1X data mode is probably unexpected, however. AT&T's LTE network won't enter testing until mid-2011.
Verizon says it has "determined the cause of 4G LTE issue & are working with major vendors to restore connections," but that post was more than 17 hours ago. In addition, the the launch of the Samsung Droid Charge, Verizon's second LTE handset, has been postponed due to the outage.
shortly after 8AM PST, Verizon Tweeted that LTE is back. Testing showed that it is, but you may have to power-cycle the radio.