Sadly no, I can't use a different folder since I have my music files (and all files) in Dropbox in order to safeguard against loss/viruses. If I move the music files to a C-drive local folder and re-route Media Monkey to find them there, if my PC dies they are lost.
Btw, Unless Dropbox or you had updates, this freeze didn't occur last year for me or user Bolsey who started this thread and who mentioned it was recent (I wonder if that helps your team investigate?)
You are more intelligent than us MiPi, I don't know how to improve the 'system call to system's open file dialog opening in Dropbox folder' and if I speak to your equivalent at Dropbox he won't be able to help as he won't know your software right? If you think of anything to try (or wording I can give Dropbox IT) please do reach out for all of us with Dropbox and MediaMonkey.