This problem has gotten SO bad for me (it got 10X worse after a hard reset last month). I'm ready to jump ship- what launcher does everyone else like? I didn't care for Launcher Pro... Thanks!
Incidentally, I found on the Sprint forums what seems to be the most logical reason for this issue- this was posted June 29, 2011, so almost a whole year ago and there is still no resolution. Absolutely unacceptable.:
Sprint Community: HTC Sense Issue Consolidation Thread
Post 24- Houston, we have an unofficial answer...
The Sense "closure issue" is do to the advanced memory managment of Android 2.3 (
http://developer.android.com/sdk/android-2.3-highlights.html) and it's Improved Power Management feature. The IPM system takes a more active role in managing apps that are keeping the device awake for too long or that are consuming CPU while running in the background. By managing such apps — closing them if appropriate — the system helps ensure best possible performance and maximum battery life.
The system also gives the user more visibility over the power being consumed by system components and running apps. The Application settings provides an accurate overview of how the battery is being used, with details of the usage and relative power consumed by each component or application.
What is happening, usually when gaming or browsing the internet, is that Sense is not 'active' during these times - think of apps that take more than 30 seconds away from the home screen - and Gingerbread kills it off thinking that it's not an 'active' app to conserve power and cpu cycles. What needs to be done, is that HTC needs to recode Sense to Gingerbread as a non-killable task. That will solve that issue pretty quickly. This wasn't an issue with 2.2 since it does not have the IPM that 2.3 does.
Currently, there is no on device fix to this issue - and for those suffering from the wall paper issue, try using smaller images - the 2.3 program loads all images in 32bit (2.2 allowed 16bit images) and it is probably having a hard time finding memory to load them. Try a stock wallpaper for a few days and see if that eliminates the problem.
So, long story short - 2.3 broke Sense (and most other replacement home screens) and there's not much that can be done until they can exempt apps from the IPM list.