UPDATE 3 (2011-07-20):
Dropbox 1.1.35 is compatible from OS X Lion.
If you’re feeling a bit adventurous, you can use the “forums build“.
UPDATE 2:
Dropbox Team Member Rian H. posted a reply assuring that the team is working to make Dropbox fully compatible with Mac OS X Lion.
“hey everyone, just wanted to give you all a heads-up that we’ll be working diligently on making dropbox 100% compatible with 10.7 over the next couple of months. stay tuned!”
UPDATE:
Apparently the current version of Dropbox caused the Finder to crash right after login.
Apple Engineers have confirmed this and recommended Developers to wait until the issue is resolved. If you are a registered Apple Developer, head to Apple Developer Forums for the discussion.
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Numbers of users are reporting they found out that Dropbox.app would not work with Mac OS X Lion.
You can’t use this version of the application Dropbox with this version of Mac OS X.
One thread on Dropbox Forums is dedicated to this issue. Dropbox user “Filip S.” came up with a solution:
I’ve figured out a quick fix for this issue. Open Info.plist inside the application bundle, and change “Bundle Version” to 2.0 . Apparently Lion doesn’t allow applications with low bundle versions to run for some reason.
Now Dropbox v.1.0.20 works in Mac OS X Lion.
Dropbox info.plist before the modification:
Dropbox info.plist after the modification:
37.294616-122.09206