"Some of the applications in your iTunes library were not installed..."

Question

"...because one or more errors occurred."
I've been getting this message for a couple of weeks now. Basically iPhone is unable to update any new versions of ANY applications downloaded to iTunes. I was hoping that 2.1 would fix this but looks like it hasn't, much to my disappointment. This is an infuriating bug. Is there anything that can be done about it? Really not happy about this.

Answer 1

I think I may have found a real solution (NOT a workaround) that both fixes the problem AND preserves specific app data, though I can't take credit for it (that belong to an Apple Store "Genius" somewhere in the US of A). It first appeared in another related thread:
http://discussions.apple.com/thread.jspa?threadID=1685284
It goes like this:
"+1. Upgrade to iTunes 8 and iPhone 2.1+
+2. Sync iPhone so you have a backup (I make a zip of my backup directory and save it off just in case - see http://tech.kateva.org/2008/08/iphone-backups-are-stored-in.html for details)+
+3. Restore iPhone to original state using the restore button on the info tab. This wipes the phone.+
+4. When the phone mounts iTunes will ask if you want to treat it as a new phone, or restore from backup.+
(An addendum: I've done a couple of restores in the past - for unrelated reasons - and have come across the "Locked SIM" and "Emergencies Only" problem after the restore. This appears to be a problem with the reset phone suddenly not recognising the SIM. I don't know if this is a widespread issue, but it certainly seems to be the case for Vodafone SIMs, but I do know that the fix is to simply remove the SIM - while the phone is on - and replace it. I might add that this is Vodefone's universal fix for all SIM-related problems.)
+5. Restore from backup. This doesn't restore everything -- but don't worry.+
+6. Sync (this will take a while if there's music involved).+
+When all is done everything should be in place. In the past the restores still left me with a lot of cleanup, but this time I only had to arrange a few icons. My passwords were restored.+
+Now, why do I think this will solve the problem?+
+When I did this iTunes said I had no updates. The App Store on the iPhone said I had 4 updates. I actually used the App Store to apply the updates -- a process that has NEVER worked in the past and has been trouble for many people. This time it smoothly applied the updates, and when it was done it said there were no more left."+
I've now had an opportunity to test this and can report success - phone now updates apps from either App Store or iTunes correctly - all the updates sitting in App Store were applied smoothly - and there's no data loss.
Some caveats:
1. DON'T attempt this first thing on a workday morning (like I did) - the process can take a long time.
2. Switch to "Airline" mode - a call right in the middle of the process will terminate it and you'll have to start over.
3. I run a Mac system, so I don't know if the fix works for Windows or other OS users. Reports back from Mac OS people are running at 100% fixed so far.
4. It appears to be the combination of the latest phone OS (2.1) and iTunes 8 that lays the foundation for this fix. Make sure you've got both installed BEFORE you start this process.
Please report back on success or otherwise.