I don't have my Evo yet so I can't and won't say this works 100% but from what I've read and what people have told me this seems to fix the problem so you won't have to do the GSM/CDMA trick anymore. Many have told me that you have to manually update this by going into -> Menu > Settings > System Updates > Update PRL
Let me know how it works out for you.
Let me know how it works out for you.