As you're running windows, I just found this in the documentation
You cannot delete Verity collections on Windows if they are created outside of the ColdFusion collections directory or on a drive other than C:, D: or E:. To use a different drive letter, edit the cf_dir/verity/common/verity.cfg file and replace an entry with the directory you wish to use
Is it your case?
Thank you for your reply, Cyril. No, that is not my case.
I have the collections in C:\ColdFusion9\collections, which I understand to be the default CF collections directory.
Also, this isn't limited to Verity; it's happening to Solr, too.
Can you check if there's anything wrong in the logs? Are CF services running with a dedicated or power user? Haven't played much with Solr or Verity so trying to find a clue... :-)
Sorry for taking so long to reply. I do not see anything in the logs that indicate what the issue might be. CF Services are running with a power user, I believe.