Near as I can tell, that error appears whenever I'm experiencing really severe latency problems. Check to make sure you're not downloading anything and that your internet connection is working properly. Run a speed test and see if maybe your connection is slow today or just plain not working very well.

I've had this problem show up when another computer on my network was eating up all the upload bandwidth for some reason, when my computer started downloading Windows updates in the background, and when my router needed a reboot. And several times when I'm in Cyrodiil.