Sounds related to this known issue, but my database entry does not mention IWP so please let me know if it applies to your situation: http://forums.filemaker.com/posts/fa2aeb70d1
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
Thanks for the reply. I suppose it depends on the definition of workspace in the IWP environment. When a portal had many records and have a editable date field with drop-down calendar activated, the calendar for the viewable records is correct but when scrolling down past the viewable records, the drop-down calendar propagates down the page beyond the viewable records. Interestingly, when selecting the portal to edit, the full web page is lengthened (by several layout pages in height), almost as if it calculated how far the calendar object would propogate down the page, while the "browsed" portal in IWP shows just "one page" length (as defined in the original FM layout). Also, this lengthening effect causes the page to take much longer to load.