In http://blogs.msdn.com/irenak/archive/2006/09/22/766164.aspx post, the following problem was described: if you have a SSRS report parameter that is multi-value and of one of the labels in the “available values” list exceeds 25 characters, the dropdown list with values for this parameter will be positioned in such a way that the end user won’t be able to see and thus select the first item. 

 

It came to my attention that there is a hotfix available that resolves this and some other issues.  For more information, visit http://support.microsoft.com/?kbid=919478