XAMPP + OS X + different root directory

[inpariswithyou]

I just purchased a Mac on which to develop websites. I've been developing on a Windows machine, and I'd like to continue using it in conjunction with the Apple laptop, so I moved my localhost files to a Dropbox folder, which works fine on Windows. When I try to change the DocumentRoot and Directory on the Mac, XAMPP throws an error that says the Root Directory must be a directory... but it is. So I don't know what to do. I've tried everything. I've googled, I've talked to Apple, I've asked friends, I've checked IRC. Anyone here have any ideas?

I'm trying to use /Users/[myname]/Dropbox/localhost as the folder, which XAMPP is insisting isn't a directory. It has nothing to do with Dropbox, as XAMPP tells me ANY other folder isn't a directory, even ones outside my Users directory. I'm running the newest versions of XAMPP for Mac and Mavericks.