Same happens to me. Like this https://www.youtube.com/watch?v=hlOLYUtT3Og
When you actually go to main menu fps is fine. But if you dont restart the game and go to server again the fps is still 1. I had this bug before 0.54 update. :(

Same thing happens to me. Was fine before the patch. Now the game runs fine when I first log in and as long as I stay in the wilderness, but if I go towards any type of town/village of even small size the lighting starts going wonky and my FPS eventually tank to around 3-5. Same blocky textures and invisible buildings as the screenshot. Stays that way until I disconnect/reconnect and in some cases I have to completely restart the client. My group said they lost their characters after the patch (they were wiped), but me and one other member didn't get wiped. We still had our characters from before the patch, and he is having the same problems. I've tried killing my character so it would have a new file but didn't work. I just have to wonder if it has something to do with us not losing our characters after the patch.

when you get this issue try:
settings->video->textures-> video memory:256MB
then change it back to what it was before

fixed it for me, but might as well not work for you

Found a fix! You need to delete everything in the launch options!
(DayZ -> Rigth click -> Properties -> Set launch options)
It needs to be like this: http://i.imgur.com/Ung7qjR.png

same thing to me, and happened before 0.54

sometimes it gets fixed changing video settings, sometimes it fixes without doing anything.

here is a video with my problem:
http://youtu.be/9hMdgcMQMPk

noscope, this might help some people, but in my case i was running the game with -dolgs parameter only (never even used other parameters than -nosplash -connect=... -dologs)
i only encounterd this issue once until now tough
wrong/outdated startup parameters might cause this issue in some cases, but not always