SOLUTION: ... (Well, at least what worked for me, and what will hopefully work for you too) 😀
Earlier today, I opened up iCloud on my PC, and found that something was quite "screwy" with the program. When I first downloaded iCloud to my PC yesterday, Photo Stream was working. As I do not have Microsoft Outlook 2007 or later, the availability to check the box next to Mail, Calendars, Contacts & Tasks is not available (although the latter have been backed up to iCloud.com, where I can view them). What I was currently left with was: Bookmarks (with Internet Explorer), and Photo Stream (the latter having an Options tab to the right of it).
Now, I must first say that my Windows Edition is not Windows 7, but it is a compatible Windows Edition: Windows Vista 64-bit OS (Service Pack 2). This difference may ... well ... make a difference for those with Windows 7, but I am not a technological wizard. (****, I just got my first Smartphone - but I am making strides in learning about this "stuff" each and every day.) In the 4th post above me (posted by 55Gala), there is picture of an iCloud Control Panel on Windows 7 that looks exactly like mine - except for the fact that in the upper right hand corner, his version of iCloud says "2.0", whereas mine says "2.1.1" - which, if the problem has to do with a necessary update, than the solution could perhaps lie there. In my case, I don't think that was the problem, because I believe that it originally said "2.1.1" when I first downloaded it. (But hey - I could be wrong. Some medications give the memory a hard time here. I will say, however, that iCloud is not listed in my history of Installed Updates.)
So ... When I first downloaded iCloud on to my PC, I was able to check/uncheck both boxes available to me, as well as click the Options tab to the right of Photo Stream. I could make changes, click "Apply", and everything was fine and dandy. Come today, however, I open the iCloud Control Panel, and despite how many times I would uncheck Bookmarks, it didn't matter. I would click "Apply", and it would automatically ask me to sign in again. When I did this, Bookmarks would be checked again. Additionally, Photo Stream was grayed out; I was unable to check the box (which was unchecked), and I was unable to go to Options. I searched the Web, quickly came upon these forums, and found a host of other Apple members having the same problem.
Somehow, I managed to get my iCloud Control Panel "unstuck", and currently, it is working fine. I did 2 "things" to accomplish this; although I must note that I am not sure if doing both solved the problem, or just the 2nd "thing" in my case. The 1st step listed below, however, is something that I haven't come across as a possible part of a solution. It is something that I just happened to stumble upon whilst searching my PC for possible fixes to the problem.
Step 1: Find your iCloud File Folder. (On my PC, I clicked the Start button in the lower left corner, then clicked All Programs, and finally scrolled down to where all the folders for various "things" are.) Click the Folder and a sub-list will appear, with items such as Calendar, Mail, etc. Right-Click the iCloud Program icon, and at the bottom of the list that appears, click on Properties. At the top, there are 5 tabs. Click the Compatibility tab, and you should see, at the top, the following words: "If you have problems with this program and it worked correctly on an earlier version of Windows, select the compatibility mode that matches that earlier version." Following these words is a dropbox underneath "Compatibility Mode", and for some reason - I have no idea why this is - the box was checked to run the program in compatibility mode for "Windows XP (Service Pack 2)". (And from what I understand, Windows XP is not a compatible Windows Edition for iCloud, so I have no idea why this box was checked.) If the box underneath "Compatibility Mode" is checked, then it is running iCloud in compatibility mode for any number of earlier Windows' Editions. Uncheck this box, click the "Apply" button, and then click "OK".
Step 2: Find your PC's Control Panel. (On my PC, I clicked the Start button in the lower left corner, and then clicked Control Panel in the list to the right.) In the Control Panel, click Programs. Under Programs and Features, Click "Uninstall a program" (and bear with me here, because you are actually not going to uninstall iCloud). Now, scroll down the list and find "iCloud". Double-click the "iCloud" icon, and a panel with 2 options should appear: "Repair" and "Remove". Check the "Repair" box, which will reinstall the same iCloud Control Panel, replacing missing or damaged files. ("Remove" will just .. well ... remove iCloud from the computer - or, if you prefer, uninstall the program.) Click Next, and the repairing process will begin and end. And that is it - you're done. Task Completed.
Well, in the end, this worked for me. Photo Stream was no longer grayed out. I could permanently uncheck Bookmarks (finally). The Options tab for Photo Stream would open. Anytime that I clicked the "Apply" button after checking/unchecking boxes, it wouldn't ask me to sign in again (only to come back to a Control Panel that looked just like it did before I made any changes to it.). And the best part: I created a Shared Photo Stream on my phone using photos from my Camera Roll (to test the program), and the Shared Photo Stream appeared on my PC's Photo Stream in no time. Hopefully, this will work for you too (regardless of the Windows Edition you are currently using).
~ Brian
<Edited By Host>