I had the same problem with my iPhone 4, my iPad 2 syncs fine however.
Prior to installing iTunes 10.3, I had turned the Cloud sync for music, apps and books on. Tried turning it off, also turned "Sync Music" off in iTunes, I was able to sync afterwards.
I will of course have to resync my music now.
i am having same issue. after adding itunes 10.3 iphone 4 will not complete sync timed out error code 50. synced just fine i hour before with previous version of itunes. i think this issue is related to icloud beta. the problem is that you can not easily remove icloud downloaded songs from iphone/ipad.just this morning i was able to remove icloud songs from my ipad 2 under itunes 10.3. however iphone 4 now can not even sync error 50. hope this is temporary. icloud should let you add and remove your music wirelessly. iam just going to use a 3rd party app to stream my music there are some good ones out there.
Also having this error. (-50) Initially it ocurred on both an iPhone 4 and on my iPad 1. Eventually, the iPhone 4 started to sync OK (after turning off the new store sliders) and doing a cold reboot.
However, neither of these efforts has helped the iPad. Only difference I can see is that I had turned on the sliders and downloaded a couple of albums on the iPad. The error occurs at the "verifying downloaded music" step.
Hope this gets fixed soon!!
This all started with trying to delete cloud songs off my iphone4. I got the same message each time timed out error 50. Strangely each time I went through the syncing process and was denied there was one less. Song on my iPhone that I downloaded off of cloud.I had 9 songs and attempted 9 syncs on the 10th time I was able sync no problem with no songs left on my iPhone. The apple IT engineer I talked to was confused and interested at the same time. Lesson do not use icloud until they figure it out.
I started to get this error when I tried syncing with my iPad 2 32GB Wifi after upgrading to iTunes 3. My iPhone 4 and original iPad does not exhibit this issue.
I fixed the problem on the iPad2 by doing a hard reset (hold down sleep and main buttons until the apple logo displays then release) and then tried syncing again (while closely monitoring the console log app on the mac for errors) with iTunes and it completed successfully.
Hope this helps someone else.
Still having issues here. Was able to sync iPhone on home iMac, however iPad 2 (which is for work and tied to MacBook Pro) backs up and goes through the sync process and it looks like it hangs when it goes to "Find purchased items" and the I get the error 50. It's not timing out, it just stops abruptly. Doesn't hang, either. Just doesn't complete the sync (which, naturally, includes podcasts, apps, etc.).
There's a difference between "beta" and "developer preview", I think. Why does it seem like something like this should've been flushed out before releasing for playtime?
For what it's worth, I had this issue too and was able to resolve it. Not sure if it's required to do everything I did or not.
What I did was:
1. Disabled music syncing entirely.
2. Synced my iPhone 4 with iTunes. This removed my music from my iPhone.
3. Turned off Automatic Downloads on the device.
4. Turned off Automatic Downloads in iTunes.
5. Rebooted iPhone.
6. Re-synced iPhone. This added my music back.
7. Re-enabled Automatic Downloads on both the iPhone and in iTunes.
8. Did another sync for good measure.
Everything seems to be working fine... the iPhone, syncing, Automatic Downloads, etc.
This is a me too, Macbook Pro on 10.6.7, iPhone 4 running 4.3.3 and itunes 10.3. As soon as I installed 10.3 tried to sync and got the unknown error -50 error pop up. I tried closing iTunes, reopening and hard booting the iPhone to no avail. Hope this gets fixed soon! Any hints would be really appreciated
Another me too...
Me on 10.6.7 MacBook Pro, but with an iPad instead of an iPhone 4 running 4.3.3 and iTunes 10.3. Same error as above; iPad starts to sync and then before it gets done backing up, I get the Unknown Error (-50) message. This only happened after I downloaded an album using iCloud. Now, as @zzmd above said, my iCloud downloads are being slowly deleted a few at a time...I'm down to 2 left from 16, so hopefully it'll start working again when they're all gone!