Is there anyway to prevent/fix this?
thanks.
In ACR, Preferences "Always open JPEG files with settings using Camera Raw". Uncheck.
And in Photoshop yet another, Preferences > File Handling, "Prefer Adobe Camera Raw for JPEG files". Uncheck.
I never could figure out which one of these actually caused JPEGs to open in ACR, so I would just check or uncheck them all. In CS4 this is mercifully simplified down to one - in ACR where it belongs.