SAS Results for uncorrected data from exemplar 2

The following warning appears in the log file

NOTE: Writing HTML Body file: sashtm.htm
NOTE: Only one cluster in a stratum for variable(s) intuse. The variance of intuse in that stratum is estimated by zero.

But no warning about PSUs that cross strata

Simple proportion internet use	
The SURVEYMEANS Procedure	
Data Summary	
Number of Strata	329	
Number of Clusters	11941	
Number of Observations	28685	
Sum of Weights	28702.2953	
  
Stratum Information	
Stratum
Index	STRATUM	N Obs	Variable	N	Clusters	
1	100A	202	INTUSE	202	202	
2	100B	130	INTUSE	130	130	
81	190G	51	INTUSE	51	4	
82	190I	10	INTUSE	10	1	
157	250Z	6	INTUSE	6	1	
158	260A	229	INTUSE	229	229	
159	260B	145	INTUSE	145	145	
329	400Z	3	INTUSE	3	1	
  Rows omitted to save space
Statistics	
Variable	Label	N	Mean	Std Error of Mean	Lower 95%
CL for Mean	Upper 95%
CL for Mean	
INTUSE	Whether person uses the --internet	28685	0.341363	0.003386	0.334725	0.348000