I'm not sure that it has been fixed in the 4.3 but this is a known problem in 4.2 seen here
Instruments
There is a known issue with the Profile action from Xcode 4.2. After a build in which no source files have changed, Instruments will be unable to gather symbols for the target application.
This affects projects where both:
- The Release configuration is selected for the Profile action.
(default)
- The Strip Linked Product build setting is set to "Yes”, or
a custom Run Script build phase strips the product. (non-default)
The workaround is to do any one of the following:
- Perform a "Clean" on the product before initiating the Profile
action.
- Do a Clean of the product and temporarily set the Strip Linked
Product build setting to "No" while Profiling.
- Set the configuration of the Profile action to Debug.
- Run successive profiles directly from within Instruments when you do
not need to rebuild. When developing Mac apps, using the GC Monitor
template in Instruments may cause Instruments to crash. To
workaround the problem please consider migrating your application to
ARC.