I too got the same error recently when I tried to install Emoji plugin. I had to reset all plugin as mentioned in above post and it took almost 5 restarts to get my site back online. As for why it is happening, I don't think I am the right person to answer it.
Some bugs I've noticed
Internet Explorer has navbar bugs, the height is pulled way out of normal range.
Internet Explorer ImageMagik doesn't seem to resize iamges properly. Left with pixellated images throughout the entire forum. Logo, gravatars etc
Twitter embed does not currently work ...I will notify plugin developer
I am currently using Nodebb 0.6.1
Can you post images of these bugs also post what version of IE you are using.
navbar height gets worse as you traverse the categories, seems to continue until each reaches the end of some other property in the css..
also that gravatar is pixellated, Imagemagic isn't resizing it well
Haven't seen any other issues with safari firefox or chrome .. good old IE
I've noticed a few ie bugs. I'm working at a training center and all pcs run Windows server 2008 R2. In IE the login button is obscured by the scrollbar. And the header is indeed larger than normal. Think the unread counter drops too. Will get a screen based shot of such occurrences. Also the background looks pink. But that's likely the small viewing angle of the monitor.