DNA degradation (from human blood) - (Aug/19/2011 )

I'm facing a serious DNA degradation problem (both smearing and ladder like pattern). the DNA that were extracted from human (with mutation carrier) blood were degraded within one month. I'm using proteinase K digestion+ phenol chloroform method, but not using commercial kit.
I use the same method for their (same person)buccal cells and saliva, the DNA were intact, a nice band was observed for all on gel.
Why can't i get a nice band for DNA from human blood like from buccal/saliva?
Anyone has any idea?

We routinely isolate DNA from blood using the phenol/chlorophorm method and I don't remember having any issues with DNA degradation over years-long storage.
What do you store your DNA in? On what temperature?

You said you observed a nice band, you mean putting just DNA on gel or PCR reaction? Did you check your DNA on gel just after the isolation to see if it didn't degraded in the process?

Your final elution or resuspension buffer probably has the most effect. I strongly recommend TE as the buffer for long term storage.

We use a commercial kit and add TE buffer at the end. We have DNA which was isolated over 3 years ago, and is still intact. Like Trof said, did you check it soon after extraction?