TM1 Web Picklist Performance

[declanr]

All,

On 9.5.2 (patched up to all but the most recent pack).

I had a websheet that contained a standard excel list (which was populated by formulas in a hidden column) that allowed users to select only valid Products based on a Brand that they were using (defined within a cell elsewhere.)
This list could on occasion have quite a few product but not monumental amounts (around 300 or so at tops), this had always worked in TM1 Web with reasonable performance... until a few weeks ago.

A few weeks ago the performance of the websheet in question became completely abysmal, all other websheets carried on as expected.

I obviously rebuilt the websheet from scratch in a few guises:
1/ Basically the same - Using an Excel List --- Awful Performance Still - Great in Excel
2/ Identical to 1 but using a subset picklist that changed via a rule based on what brand the user was using --- Awful Performance for TM1 Web - Great in Excel

Option 3 works at lighting fast speeds, I have a process that creates dummy dimensions for every single brand by a series of while loops, the websheet then just looks at said dummy dimension with a subnm. I don't mind using option 3 as it is actually sort of prettier for the user since they get to see the full hierarchy etc for their brand.

The question is more over has anyone else noticed a change in performance when using lists or picklist in tm1web lately. All I can think that has changed is a patch to Excel 2007 on the TM1 Server around the same time.

Any ideas would be appreciated, its not urgent but just my curiosity really.

Thanks in advance.