Delay in Biometric request letter --> Any advice

[23367]

Current vignette HSMP / Tier 1 : TIER 1 GENERAL (+1 dependent)
2. Date of expiry of current leave (visa) : 30/01/2012
3. Date application posted : 15/12/2011
4. Date on which Application delivered at UKBA: 16/12/2011
5. Date payment debited : NA
6. Payment mode : Postal Order
7. Acknowledgement received: 22/12/2011(dated 19/12/2011)
8. Biometric letter received : TBC
9. Biometrics provided : TBC
10. Date (new) leave to remain valid from: TBC
11. Date passport and letter of approval received:TBC
12. BRP received: TBC

All,
I had submitted by application on 15/12/2011. I received two acknowledgement letters. one on 22/12/2011 and another one on 13/01/2012. No idea why i have received the second acknowledgement letter even though the reference number is same in both the letters. I am yet to receive the Biometrics letter. it is almost 45 days since i posted the application.

Is this a situation faced by me alone or is it common? has anyone received 2nd acknowledgment letter?
Guys, Can you please advise if something is wrong?

Thanks

[QuickSam]

Typically you should get it within 4 weeks but in some cases the Biometric letter can take up to 6 weeks.

Hope you get yours soon.