In Unity 4.5.0f6, I get an exception building for Windows Store:
Error building Player: NullReferenceException: Object reference not set to an instance of an object
Build Settings:
Windows Store Apps
XAML C# Solution
SDK 8.0
No other checkboxes checked
The above error is the only line I get. Everything was fine in Unity 4.3. Which additional information can I provide to help you with this?
Please attach Editor.log
Hey Tomas,
please find attached the editor logs and DxDiag.
Blind guess, try going to Player Settings, and recreate certificate by click “Create” button.
Nice shot, the certificate was missing indeed! However, the error still persists… New logs attached.
Any updates on this?
It would be easier to tell what’s happening, if you submit a bug report with your project. Log file doesn’t show any specific issue.
The log shows same NullReferenceException, so do as Kazimieras suggested, submit a bug
Alright, here it is!
http://fogbugz.unity3d.com/default.asp?611114_mfg1p9ealdm5tt7a
I got the same issue. Switching to 8.1 solves it, but that’s not what I want to do (want to support both 8.0 and 8.1).
By the way, I have both VS2012 and VS2013 installed as well as a system that was upgraded from 8.0 to 8.1 (a long time ago) and was able to successfully build everything with Unity 4.3.4.
Found the error: the “Override Background Color” toggle causes it. Disabling it makes the build work as normal.
The fix for this issue is available in a patch “4.5.1p2”. A patch can be found here:
Hmph, I think that fix will be only available in 4.5.1p3, not 4.5.1p2.
I got the same issue in the lastest Unity 4.6.3 
This issue was not related to iOS in any way, I suggest you open a new thread
Apologies, I didn’t notice when I posted this was in the Windows section - so I’ve deleted my post. I’ve since found that 4.6.3p1 has probably fixed my problem, and so far so good.