Over 6 months ago I blogged asking StumbleUpon to please stop lagging me.

Ever since they had launched their redesign into beta, I was being plagued with insane performance issues in which my entire browser would lag to an almost stand-still after visiting my profile or inbox at StumbleUpon.

Here is a video capture I took of the toolbar freaking out. You can get an idea of the lag it causes by how slowly the bar is jumping to the right and back.

[flickrvideo]http://www.flickr.com/photos/weirdasianews/3252766034/[/flickrvideo]

Of course I was in constant communication with some StumbleUpon folks who worked on the toolbar, and they would try their best to understand the issue. They released many potential fixes, but indicated since they could not recreate the problem, it was hard to offer a solution.

During the recent release of a new toolbar build, StumbleUpon mentioned some adjustments to their options, so I went to take a look at the new changes.

It was then that I noticed the ‘prefetch stumbles’ option, which I had turned on many months earlier.

Note the option indicated that it ‘makes stumbling faster’… 🙂

It then occurred to me that if I had some 20+ browser windows open (which I often do) and they were all trying to pre-load multiple pages each, then it would probably cause the lag that I was experiencing.

Sure enough, as soon as I turned this option off, I never had the ‘stumble lag’ again.

I quickly shot a message over to the guys at StumbleUpon and got the following response:

“40-50 windows? Yeah, that could do it. Hadn’t even considered that scenario.”

So if anyone else out there is struggling with an unexplained super lag and you happen to have the ‘prefetch stumbles’ option on, at least you know what the problem is now.