Thank you for your post.
I cannot duplicate the problem. This is what I have done:
1. I launched FileMaker Pro 10 on my iMac running OS X 10.5.6.
2. I pulled down the File menu and selected "Open Remote..."
3. I selected a file over the network and opened it with limited access privileges.
4. I went into Layout Mode, selected a field, pulled down the Format menu and selected "Set Tooltip..."
5. I entered the formula "Self".
6. I went to Browse Mode, put my cursor over the field, and the Tooltip appeared after 1-2 seconds.
Let me know what I'm doing differently, and I'll try to duplicate it here.
If you are doing similar steps, is this only happening with this one file? If you create a new database file locally, do you run into the same problem?
Any additional information you can provide may help narrow down possible causes.