OK, so it seems to have been resolved… at least for me. According to Bloglines:
“We believe the problem has been fixed, and regret any inconvenience this issue may have caused you. Please let us know if you have any additional questions.”
And since then, my blog has been getting updated within a few hours.
Of course, the fact that I pestered them may have had something to do with it.
Whatever the reason, it works for me now.