Can I refresh thumbnails

Ummmm...

Why? What's the practical problem that you're attempting to solve?

gwm2:

Launch iPhoto with the Command+Option keys depressed and follow the instructions to rebuild the library and select the options relating to the thumbnails. I'd also select the database option also.

Do you Twango?

TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've written an Automator workflow application (requires Tiger), iPhoto dB file backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.

G5 Dual Core 2GHz, 2G RAM, 250G HD; G4 Dual 1Ghz, 1.5G RAM, 80G HD, QT 7.1.3, Mac OS X (10.4.8) 22 LCD, 200G/160G FW HDs, Canon SD700IS, i850 & LIDE 50, Epson R200, 30G iPod

Does Automator work with iPhoto v5.0?

iMac G4 Mac OS X (10.4.9) 700 MHz, 40GB HD, 512 RAM, 250GB Ext HD