Drag and drop issue on Premiere Pro timeline

Hello,
since yesterday, I've had a big problem with Premiere Pro: I'm unable to drag and drop elements to the timeline. Every time it's the same thing: I can click on the elements in the project panel, but as soon as I try to move them, a hand appears with a no entry sign telling me that I can't move the elements, and then the software freezes and I have to force quit it...
This is the first time I'm working on an important edit that lasts over 10 minutes, but I specifically bought a good computer for this, so it should work. Yet, I feel like the software is lagging a bit. However, when I check the settings, only 2% of my CPU is used and 22% of my memory, so there shouldn't be a problem... Do you have any ideas on how to solve my issue, please?
Thank you in advance,
Aurore