I haven't experienced that and I've recently had to do a lot of testing of file upload scripts in Safari and Firefox. Maybe check with software update and make sure you have the most current version of Safari?

Definitely got the most recent version - just checked.
Its a problem I've been having for a couple of years now, since I moved back to using mac's.

Unlikely to be a Safari issue, or there would be thousands of reports of the issue

I would look for a bottleneck in your connection, which can cause the upload scripts to time out at the server side.

If you're connection can't upload the file quick enough, the server will time out and may not send the correct response back to your browser, leaving it hanging.

Just a thought.

Yes- "safari hangs". this is a chronic problem w/ safari ( along w/ "safari crashes" & "safari won't quit". I read about it while googling for reports & fixes for the other 2. Finally, it started happening to me. Now, it only happens occasionally. I find that closing the page (works best if it was opened in new window) then going back again oftentimes pops the page right open. It's damned annoying. It seems to have started after a software update ( this isn't for sure though. I might be swayed from having already read other reports say this).
Best policy is to do all housekeeping. Use 'reset safari'. W/safari turned off - Trash the com.apple.safari.plist file in user/library/preferences. (manuals advise to save a copy to the desktop renamed w/ a .txt extension in case you need it. After restarting safri succesfully, just trash the copy too.). I also trash the cache folder for safari.
Most importantly, when doing software update, run 'repair disk permissions' before & after. Also run chron jobs. Do all the tidying up you can. This usually mitigates these problems safari pops up with, if it doesn't solve them.
also, i have heard that many people do not like to restart their computer very often. It is quite amazing how many oddball problems doing this can solve :-)
- just for the record; Safari crashes when you use command-w to close a window & then click on an underlying link just a little too fast. / safari won't quit' after using the save image command ( & possibly others) over & over. Quitting starts a cpu/memory use spike & safari just sits there, really really slow gobbling up resources doing nothing. W/safari turned off -Trash the icons folder in user/library/safari. ( plist files & cache folder & the icons folder in safari are rebuilt when app is started again.)
- i haven't read of an explanation or solution for the loading problem yet. It does go away, as mysteriously as it came.

i have heard that many people do not like to restart their computer very often.

If it wasn't for software updates I would probably restart my computer less than once a year. :D

thank you commanderW.
At least I'm not going mad! I couldn't find anything myself on this subject in google.
Will try the trashing of com.apple.Safari.plist and see if that helps.