[XPERIA X10 General] k1sr:
There's a lot of threads about issues after the 2.1 update, but not too many solutions... Thought I'd start a thread and collate all the solutions as a quick reference.

DO NOT POST PROBLEMS OR QUESTIONS HERE, JUST SOLUTIONS TO COMMON PROBLEMS IF YOU KNOW THEM

Example (and please use the exact same format if you want me to collate them into the start of this thread)

PROBLEM: Brief Title for Problem

DESCRIPTION: A more detailed description of what exactly the issue is

SOLUTION: Simple solution on how to solve the issue - include steps where required

AND NOW THEM ALL TOGETHER

PROBLEM: 'Wrong' Contact Pictures

DESCRIPTION:The 'social' phonebook means all my contact pics are facebook pics instead of the ones I want.

SOLUTION: When you edit a contact, you'll have a number of headers for where the information is taken (Gmail, Facebook, etc.) - if you tap the Gmail picture, you can (a) select whatever pic you want, and (b) select 'set as contact picture'

PROBLEM: Facebook Contacts in Phonebook

DESCRIPTION: Instead of just proper contacts in my phonebook, I've now got 400 facebook contacts in there too.

SOLUTION: Tap the 'contact groups' icon up in the top left of the phonebook (image of 3 heads) - now, under display contacts, tap the Facebook groups and unselect 'all contacts'

PROBLEM: Can't restore contacts

DESCRIPTION: I've tried a number of time to restore my contacts, but there's nothing in my phonebook... strangely my missed calls and messages show contact names.

SOLUTION: Not sure if this is and actual solution, but try tapping the 'contact groups' icon up in the top left of the phonebook (image of 3 heads) - now, under display contacts, tap the Gmail group and select 'all contacts'

Edit - you might still find that not all of your contacts are showing up - strangely I checked again, and the option changed from 'all contacts' to a large list of different groups under google contacts - just tick all the boxes

PROBLEM: Duplicated details in contact

DESCRIPTION: After restoring my backup, all my contacts have their phone numbers, etc. duplicated - e.g. 2 x their mobile, 2 x their email, etc.

SOLUTION: This is the result of multiple attempts to restore your contacts (per above) - delete all your contacts, restore ONCE, then if they're not showing up, tap the 'contact groups' icon up in the top left of the phonebook (image of 3 heads) - now, under display contacts, tap the Gmail group and select 'all contacts'

PROBLEM: Low Resolution Contact Pictures

DESCRIPTION: After restoring my contacts, all the pictures are low resolution

SOLUTION: Backup seems to only backup the a low res image - you'll need to re-do your contact pics. Open up and edit your contact - you'll have a number of headers for where the information is taken (Gmail, Facebook, etc.) - if you tap the Gmail picture, you can (a) select whatever pic you want, and (b) select 'set as contact picture'

Edit: Full screen image (like when someone calls you) doesn't seem to display quite as good images as in 1.6, but this method certainly improves them (especially on the contact details screen) - I'll update if I find more info

Edit - apparently, there's no real solution: http://phandroid.com/2010/04/13/images-look-blurry-on-android-2-1-theres-a-reason-for-that/ - you can use facebook contact, which will give you a better image, but it might not be the one you want, and it also doesn't seem to connect to 3rd party apps either

PROBLEM: No Auto Brightness

DESCRIPTION: I can't set Auto Brightness anymore - only fixed levels of brightness

SOLUTION: Auto Brightness seems to have moved to the Power Control widget - there is a brightness setting which has 3 modes - Low, Auto, Bright - toggle through, and leave it on the one after Low - that's Auto. Note, it doesn't seem to be as good as it used to be in 1.6, but at least it's still there... The plus here is that Auto never went as bright or as dark as you might have liked, so now really, you have more control...