Is there a limit to the number of data points that can be analyzed using Analyze/Multivariate/Cluster? I have a set of 72 rows x 72 columns, and when I run a hierarchical clustering analysis, only about 25 of the rows are included.
I have used cluster with a lot more than 25 rows before, and the Statistics and Graphics Guide says that hierarchical clustering should work up to around 1,000 rows. I assume you haven't excluded the points that don't show up in your cluster and that they aren't missing data in the column(s) you are trying to cluster around.
Are there any other platforms that don't seem to be working right?
Do the blanks correspond with the rows that don't show up in your cluster analysis? If they do and the missing data is in columns that you are using for the clusters, that makes sense. If they match up but the missing data shouldn't be needed for the cluster analysis or if they don't match up at all, you may want to call tech support or post a bug on the knowledge base.