I went through a process of steps and mine seems to be working GREAT, just to be complete on what I did I will list everything, not knowing what may have helped it.
I installed a ringtone manager (free) from a member over at xda. Once installed you can select the second tab to assign a ring tone for every contact you have.
http://forum.xda-developers.com/showthread.php?t=309837
(link for the ringtone manager)
Second, I installed the DiamondTweaks cab so that I could edit the 1.4 Mute line that we were told to do.
Third, I made the volume control the single control HTC bubble.
Fourth, I installed the badboy audio fix that was posted a few pages back I guess it restores the audio setting for winmo or manila, not sure.
I did it all in that exact order, the ringtone im using was made with the MP3 Trimmer app from my music folder on my SD card which I saved into Windows/Rings after I converted it to a smaller size.
I have called myself from GV multiple times after making changed to Sense 2.5 and installing different cabs, making changes to S2U2 all without a S.R. and it works perfect. Of course I did finally do a S.R. and it still works great, even some of my contacts have called and it has yet to get corrupted. *Crosses fingers* I hope i didnt just jinx myself.
Like I said, im not sure which steps did and didnt effect the outcome but im rolling with ringtones baby. Also on 21864.