You might try turning off GPU acceleration in your Lightroom preferences. On these 41 MB files, what export items are not available? Are these raw images, or some other format? What OS are you running?
I am on Win7Pro. (8coreI7, 64GB RAM, 2 Nvidia, SSD C and D, striped RAID for video, dedicated HD for images).
I played around a little- it is graying out size changes, metadata, sharpen and watermark, but ONLY if I don't change the format. It matters not if it is a jpg or Canon or Nikon raw, even a psd; if I change the format I have access to those controls. If I don't change it I can't.
This turns it into an annoyance, as I can convert to psd or tif to get it into Ae or Pr, or into Ps where I can resize.
But I'm disappointed in Adobe, Lr CC is a step backward, and it's slower. That's bad for any software, unacceptable to people using it to make a living. If I'm working with a client over my shoulder and I keep getting error messages that can't be cleared (software is busy) I look like an idiot, or incompetent.
I don't understand what you mean by not being able to change the size. The only way to do that would be to export a copy with different settings. I'm having difficulty relating to your other problems because I haven't had a single problem with Lightroom CC since I installed it.
It won't let me change the settings. It Lr 5, 4, 3 and 2 did.
I guess they need customers smarter than I. Or customers with more powerful computers. Or both.
Thanks for the suggestions, I'll muddle through.