Sorry, I have no solution for this problem but at least the list gets bigger.
I've been using iCal 4.x for adding files to my events. I was also able to share those
events ( including attachment ) with my customers.
Today I was looking for an old event + attachment but there was no attachment and not even an information that there might have been any attachment. A link to the file would have been pretty helpful.
Of course, I can find all files but it will take hours, days, weeks to fix everything.
I do not expect any message like " Dear Customer, The world's most advanced desktop OS & online storage service is now available! Oh, btw: you will not be able to add attachments to iCal events anymore using iCloud..."
But an information, somewhere inside iCal, about such issues helps preventing instead of fixing afterwards...
I just found this out after talking to Apple support and then I searched the forum and found these posts. I was using iCloud to push everything to my iPad and keep my calenders in sync. Can't do it with iCloud calendar selected, it has to be on my Mac Calender for the "Attachment" option to appear. Note: you can logon to your account on iCloud and add attachments there but it won't push the attachments to the Mac nor iPad.
I asked the Apple Rep to bring this to Management's attention.