Can't speak to Win 7 specifically, but the behavior you're describing is network / bandwidth related. FileMaker is attempting to download all the records on the report from the server when you grab the scroll bar and drag it to the last record. It's waiting until it receives the last record to refresh the screen. Your assumption about timeout is probably either on the mark or very close. It's taking so long for the entire record set to download that Win 7 is getting impatient and shutting down FM before it has a chance to finish.
You might be able to reconfigure your report to speed it up to avoid the issue by moving some of the fields out of the report table, thinning down the graphics, or using a Virtual List technique. This might allow FileMaker to finish what it's trying to do before Windows decides to cut it off at the knees.
Thank you Mike!
I have discovered just a few minutes ago, that the antivirus might be shuting down the network because "heavy traffic to a not responding process" could be interpreted as malware. The antivirus this computer has is ESET NOD32. There is a section that states web protocols filtering and I excluded the IP address of the server, so it does not apply any kind of filtering to the comunication to FileMaker Server.
To my suprise, even though the "Do not respond" on the title bar still appears, Filemaker Pro can do the report and the "Communication with the host is lost dialog " does not appear.
I thought this issue was resolved with the antivirus setting. However. It is not.
Today I got the error back on all Windows 7 machines. One with windows 7 Ultimate and one with Windows 7 Home Edition. The report works fine on Windows XP and Mac.
I think I can explain the whole issue. This may help to trouble shoot similar problems in the future.
The main inconvinient in the report I was generating was the size of the images in it. Each page has at least 8 pictures and information from many tables. As a footnote, combining many tables into one, or use virtual list tecnique did not show any difference in this specific situation.
I was under the impression that FileMaker Pro scaled any image to the size it was presented. I wrongly thought if the image is about 1024x768 pixels but the container is shown at 128x128, FileMaker Pro would scale the image to 128x128; however, it is not the case. The image is shrunk only in appearence but the real file remains. This leads to an enourmous use of memory while generating the report.
Using "ProcessExplorer" on Windows, I saw how memory was retained but not released as the report was being generated. When memory was almost full, FileMaker showed the message "Connection with host was interrumpted and could not be reestablished". I though the message was triggered by network issues, but it seems the error was caused by low memory in FileMaker Pro which made the network module stop functioning.
This was overlooked, mainly because the report could be generated on an old Snow Leopard machine (Macbook Pro, Core Duo) with 2 GB RAM, while it could not be created on a Windows 7 Ultimate machine (new desktop iCore5) with 4 GB RAM. Windows XP machine, Dual Core, 2 GB RAM could generate the report only the first time. Save as PDF was impossible on any Windows machine. Definitely, FileMaker Pro in Mac OS X has far better memory management.
I decided to create a new container field with an optimized thumbnail using GetThumbnail (field, 128x128) just for the report and the error vanished completely. Also, PDF generation, that was impossible in any Windows machine, can now be done perfectly. The previous PDF report was about 300 MB, the new PDF report weigths only 15 MB.
Of course, retooling the report also benefits the old Mac, which now creates the report 10x faster!