Just played around with it some more and part of the problem is having Newsblur set to load the oldest article first. If there are a lot of unread articles, say in the hundreds, it cycles through the load process from newest to oldest. Since loading new articles is already slow, the browser sits at 100% CPU usage for several minutes as the entire list of unread articles loads.
The good news is that I am going to be rewriting a significant part of the front-end story loader as part of a Backbone.js-izing of NewsBlur that will take the next two months.
But for now, you can at least get away from switching to only view a single story at a time (change it under Preferences). It’s not ideal, but that way only a single story will be loaded at any given time.
It takes ages to load and I hear ding dongs through my sound card, I already have it set to single story, but that makes no difference, I also have the unread only button selected and unread oldest in the feeds selection window