GT,
I know this has been open a while now, but thought to share my own experience of this.
I had a document, which had 2 queries.
Both queries had the same dimensions, but measures from different fact tables.
Dimensions from both queries were auto merged (as auto-merge was enabled by default).
I had created a multi value list Input Control on a dimension from Query 1.
Report worked fine for a while.
A while later, my Input Control seemed "corrupted", and would mysteriously change into a Single Value Entry Field control.
The report would also constantly give a "An internal error occured while calling 'processDPCommandsEx' API. (Error: ERR_WIS_30270)(WIS 30270)" error every few minutes!!!
Thereafter, I could not create a multi value list Input Control at all, as I would only get the Single Value Entry Field option as shown in your screenshot.
I later traced this to the fact that after some test data loads were done into the datawarehouse, one of my queries now returned10.2 million records, whereas the other query returned a 'normal' 10 thousand records.
The merging of the dimension used in the Input Control was therefore somehow compromised, causing the issue.
I simply unmerged the dimension, since I only needed to show data from one query at a time.
I believe there may have been too many miss-matches on that dimension. I probably could have enabled "Extended Merged Dimensions" to also resolve the issue, however in my case I didn't really need the dimensions merged.
Issue resolved.
I would advise anyone to look at the "weighting" of the queries whose dimensions are merged if this strange behaviour occurs in your Input Controls in Rich Client...
I hop this helps
Lawrence
Tricord BI