At some point I defined an index that included all the files in a folder on partition T.
As soon as I did that, ALL my "containing text" searches stop making progress before they completed. Note that I wasn't (intentionally) searching the index (I was in Expert mode, not Index mode), and even "containing text" searches on other partitions (like partition C) would not complete successfully.
As soon as I deleted the index, the "containing text" searches worked fine again on all partitions. Why is that? Any ideas?