Have you tried resetting the preferences?
You should also update to the latest version, 2015.4.
If you have problems updating, download from here; Keeping Lightroom Up-to-Date
I've done that several times and I am running the latest version. I literally can find no legitimate help on this issue anywhere.
Do you have Read and Write permission on the folders you are importing from/to and exporting to?
Have you tried running Lightroom as Administrator?
I've triced or verified both. I wonder if there is some odd software conflict causing this. I have to use this computer for other things and not just LR. No other software that I use is having this issue.
Also, the hanging is not always consistent. I attempted to export a set of pics to a folder on the desktop this morning. The first attempt stopped responding with nothing being exported so I had to kill LR. The second attempt created about 1/3 of the images and stopped responding. The third attempt worked.
I also wonder if there is a way to demad a qualified person to review this problem at Adobe?