Hi Laura,
If you're not receiving an application error when the crash occurs, its unlikely that a crush dump is getting created--- However, to double-check go to the following directory: C:\Users\USERNAME\AppData\Local\ESRI\ErrorReports. If you see dump files here with the dates of the crashes you've experienced, reach out to Technical Support and we can investigate further for you.
Something else to consider since you mentioned that this issue wasn't occurring previously-- check to see if there have been any recent updates to your anti-virus software or trusted sites list. Also, a few quick tests might help narrow down the cause:
1. Are you able to sign into ArcGIS Online through a browser?
2. If you test the same workflow with your anti-virus disabled (only as a test), does the crash still occur?
3. Do you see the same crashing if you login using a different Windows User Profile?
4. Is your graphics card driver up to date?
Let us know if the issue continues to occur as we're happy to help!
Thanks!
Kirsten