When I try to import photos into lightroom lately, most of them are greyed out and cannot be uploaded. When I select the few that are available, they begin to upload and sometimes a few do but then it gets stuck saying "uploading" forever and I just have to quit lightroom. I have tried with RAW and JPG files and both from SD cards and directly from my computer
Greyed out photos means you have previously imported the photos into Lightroom, and there is no need to import them again (nor is it a good idea to do so). You need to go to the Library Module (not the Import dialog box) and find the photos and use them as you want.
If you try to import a not-greyed-out photo, and it takes "forever", close Lightroom and try deleting your preference file: Preference and other file locations in Lightroom 5