It could be all of the above. I think a clue you gave us is that goes into a craze when you open the application which makes me think that it's a chart expression working with a badly connected datamodel.
Do you know how many rows are in the application? You can use this snippet to find out how many rows live on the tables:
Too much data?
for i = 1 to nooftables() - 1
LET tableName = tablename(i);
LET numberOfRows = NoOfRows(tablename(i));
Trace(Number of Rows for $(tableName): $(numberOfRows));
next;
Expensive Chart Expressions/Bad Data Model:
I'm not sure of a measure that QS has concerning how expensive a chart and it's expression are. But I have had issues whereby I thought a table was connected through a key, and they really weren't, and that caused my calculation and SetAnalysis to go haywire. Haywire to the point that the chart would run out of memory for it's calculation.
This can also be caused by unclean data. For instance, I've had data where the key was "0" for tons and tons of records. This meant that when my chart was doing a calculation, it was pretty much cross-joining the tables.
Hope that helps, let us know what you find. If you are feeling frisky, duplicate the dashboard, and then begin a binary search by culling half the sheets and seeing how it performs. That should help you decide whether it's a UI only problem, or a dataset problem manifesting as a UI problem.
