I’m having the same problem at
https://www.cranehanabooks.com/blog
Unable to upload new images, can’t access media library. No useful error message, just ‘there was a problem uploading, try again later’ message.
Problem either started with changeover to WP 4.4.1 (which I was delayed a month in deploying, since a previous WP update crashed my site in early Dec.) I installed BackUpWordPress to help safeguard my data in early January after restoring the site.
I’ve already sent email to my site host (Domain.com and iPage) earlier today, no response yet. I’ve cleared what caches I could. I’m aware that this is probably going to take someone whose coding skills are beyond mine, and I just need to get a clear process for them to follow this weekend when we have time (I’m on 12 hour shifts right now.)
A fix is getting time critical in the next two weeks, since I’m having a book and art gallery launch in early Feb, and need to advertise images. My worst case solution will be to switch over book and gallery promo to my Tumblr site.
Thanks so much for anyone’s and everyone’s help.