I assume that's caused by the same reason, which makes your UIs have this incorrect gradient. Something is messing up the initialisation of Prism when you launch Houdini.
Can you check that there are no deprecated Prism files in your Houdini preferences? There should only be a single Prism.json in the packages folder. Older Prism versions had code in \python2.7libs\pythonrc.py or in \scripts\456.py, which could cause problems if it's still there.
I assume that's caused by the same reason, which makes your UIs have this incorrect gradient. Something is messing up the initialisation of Prism when you launch Houdini.
Can you check that there are no deprecated Prism files in your Houdini preferences? There should only be a single Prism.json in the packages folder. Older Prism versions had code in \python2.7libs\pythonrc.py or in \scripts\456.py, which could cause problems if it's still there.