Report Manager Performance (or lack thereof ?)

i am in the process of creating some new reports on a new Reporting Services site

reports developed in VisualStudio2005 pointing an an AnalysisServices Cube on a (development) SQL2005 database

when i Preview the reports in Visual Studio 2005 on my development box, the reports take about 12-15 seconds to run (about 4-5 seconds before the "Report is being generated" logo appears, then another 8-10 seconds before the report appears (report is a series (1-8) of charts))

when i run the same report (with the same report criteria) via the Report Manager (pointing at the same AnalysisServices Cube), it now takes about 45 seconds to run (about 15 -16 seconds before the "Report is being generated" logo appears, then another 30 seconds before the report appears)

(n.b. this is not due to initial Report Manager start-up delays, the timings are for the second and third run of the report)

can anyone out there point me in the direction of where to look ?

also

have just had a look at the entries in the ExcutionLog table of the ReportServer database

ran the report - it took c. 30 secs to run & render

in the table

TimeStart 18/04/2007 1:20:48 p.m.

TimeEnd, 18/04/2007 1:20:57 p.m.

TimeDataRetrieval 187

TimeProcessing 539

TimeRendering 210

dont know how reporting services thinks it did it in 9 seconds ?!?!?!?!