Adalgar

Though lowering the [TerrainManager] settings in SkyrimPrefs.ini does help, I wasn't happy with the less distant detail. When only lowering the fTreeLoadDistance to a value of 55000 there were significant less trees in the far distance. So I tried something different. Since my set-up probably is script heavy I upped fUpdateBudgetMS in Skyrim.ini to 1.6. Please see Papyrus section in Skyrim Stability Guide for information - http://www.nexusmods.com/skyrim/mods/50244/? I've set [TerrainManager] settings back to ultra and thus far it seems to be much better while again horse riding for an hour. Of course, it could also be just a coincidence.

Yep, works for me too. Tested for an hour non stop horse riding. Hardly a hiccup, smooth sailing. System pretty much similar like njkilleen's and scorpgul's. ENB, DynDOLOD, lots of mods. BTW - for reference - when you set DISTANT OBJECT DETAIL to high through the skyrim launcher it will halve the shadow draw distance when shadows are set to ultra, so best change it in skyrimprefs.ini so one can still have the 8000 shadow draw distance. Thanks for posting, both njkilleen and scorpgul, and for looking in the right direction and finding the culprit.