Bug shader graph window does not respond at all

i have been working with shader graph and HDRP quite a while when suddenly the shader graph window stopped working. it simply does not respond anymore at all.
actually the entire window the shader graph tab is added to does not respond anymore so i am not even able to switch tabs.
i guess i have tracked it down to the point: "bounding box" in the ui elements debugger shows nans for the parent panel container cuaing the issues and the console showing:
Pixels per point should be positive
UnityEngine.GUIUtilityrocessEvent (int,intptr,bool&)
nans on "bottom" and "right" seems to be ok tho as i also get them in other projects where the window just works.
i already deleted the entire library and reimported the project without any luck.
any advice how to fix this issue?