It is working fine at my end.
Could you please try doing the same in a fresh new muse file.
I am saving the projects as a new site by using "save as" ... isn't this pretty much the same procedure
by saving the site under a new file name?
So it looks like there is some corruption in the file itself.
That's why I asked you to check in a new fresh .muse file.
I give it a try later on. Maybe it has something to do because I locked and unlocked the guides manually via "> Object > Lock".
You can lock guides individually via > Object or lock all guides via > View.
Whatever, I tried to copy&paste in place from one master page to another master page but it caused Muse instantly to crash.
Ok, so new site, master page, placing some guides, copy guides, and then Muse is suddenly asking me to save the site?
Why does this dialog box appear anyway just because I am copying some guides?
Looks strange, so do you get this save option every time you copy the guidelines or just the first time?
Indeed, every time ... I don't see a reason why a save dialog box should appear by copying guides.