Qiagen high speed maxi

[Steve Crampton]

We have been using the Qiagen high speed maxi prep kit to isolate  
plasmid DNA for a while and have had some problems.  We have  
standardized our growth time and pretty much always prep high copy  
plasmids such as PcDNA.  The problem is that sometimes we get 1 mg of  
DNA and sometimes we get no DNA at all!  My wife (in a separate lab)  
has also had this problem and they did a side by side comparison (2  
different columns, same cultures, etc) and one had 0.8mg and the other  
no DNA.  Has anyone else had a similar yield problem with this kit?
Steve Crampton