MY Dear same problem I had before. But Now I am enjoying OS 6. I updated may be 20 times but after that same OS 5 was found SO Want to share with you my experience.
1. Back up your contacts, Messages, mails etc by using Blackberry desktop software.
2. Close BB desktop software
3. Download & install BBSAK software, you can find it very easily through Google.
4. With BBSAK software wipe your device. (It will erase your OS 5, This is what I think you are not doing)
5. Insatall os 6 BY using BBSAK or directly from C drive location.
6. Dont not disturbe the process, wait until it gives you confirmation of successful installation.
For any assistance mail me at
If successful also mail me at same address.
Thaanks & regards,