What's ugly about it?
In any event, Premiere Pro's built-in monitors are not for judging quality, only for viewing content. There are many ways the image can appear degraded in those Monitors, so if it exports fine, then this is not something that needs to be worried about.
Thanks for your fast awnser.
The exported clip looks as ugly as the one in the built-in monitor.
Only the exportet Frame ("Export Frame" function in Premiere) looks good.
How fast were you panning.
Can you upload the clip?
I'm with Ann, the clip itself might help. I just don't see anything amiss with the still you posted.
I see a pretty bad image with lots of blocking.
In other words, totally unacceptable. If your exported video looks like that, perhaps it has something to do with the interlaced footage. Since you are running this at 400%, maybe if you got rid of the interlacing prior to speeding it up, you might get a better result. Although, to be honest, I can't recreate this with HDV or AVCHD. I click on the camera icon halfway through and get a perfect picture. My monitor looks bad if I set it to see both frames instead of just one, but the export is fine. My video export is also fine, and considering I used pretty shaky video for this test, I would have thought that a problem would show up.
I hate to ask, but could you check again that your video exports OK at 100%. Also, are you exporting to interlaced, or to progressive? What is the ultimate destination for the video? Television? YouTube? A DVD?