During some games, my mouse cursor changes to some strange dotted line (like in the picture). It looks like that, but I had to draw it myself as the cursor is not visible in screenshots.
This is really bothersome as I do not see the exact point where I am clicking. Furthermore my mouse stays this way even if I Alt-Tab or close StarCraft entirely.
How can I prevent this and is there a fix except restarting my computer?
This happens in various games, and not just in games. It is most likely a hardware related issue. There are a few things you can do to either fix this, or confirm what is causing it.
Before doing anything, update your video card drivers. Visit your video card manufacturers website and download the latest drivers.
If the problem persists, you can boot into safe mode and try to reproduce the problem. Seeing as in your particular case the problem only occurs while playing Starcraft 2, you may not be able to reproduce the problem. However, if you do reproduce the problem, there's a very good chance your video card is on its way out (AKA it's dying). If you don't want to purchase a new one, you can wait and see if it dies, and just live with the issue.
One last thing you can try is to change the Window's mouse style. I don't own SC2, so I don't know if it uses a custom mouse. But it's a simple change and worth a shot!
However, one thing seems clear: This isn't Starcraft 2 related, or even video game related. It is probably OS or hardware related. You can try and Google this yourself and see if you can find any solutions. It seems to me like the memory where the cursor is stored is being corrupted, causing it to draw incorrect information. This behavior may be triggered by SC2, but the problem lies within the video card memory.
In response to Ender (I cannot post comments yet!):
The reason I say that the video card may be starting to 'die' is because artifacts like this appear when your card gets old and is ready to go. This is a graphical glitch that is not game dependent, or OS dependent, because I've seen it on XP and Windows 7. That leaves the video card to blame (I rule out the actual image file begin corrupted because this will happen with any cursor image). Before my old graphics card died, weird things like this would happen. I would get textures in games that were offset, and you got strange lines and dots in them. Some textures would also discolor, and I'd even get polygons ripping across the screen. After this, my video card died, and I had to purchase a new one.
Without proper image of the cursor in its glitched state, its hard to tell. A possibility is that one of these artifacts causes the cursor to shrink into a bunch of very small cursors. They would appear as a line of very small dots. Things like this I have also seen appear in games when your card is on its last legs.
There is indeed a quick fix to it. But it is not a permanent fix. If you are using Windows 7 hit windows key + r this will open up a window where you can start a program, type main.cpl this will open a window where you can change options for a lot of things. What is of interest to us is the mouse of course so go to pointer options. Ok once here you want to check "Display pointer trails" and i usually put the slider to short cause this thing pisses me off. With the slider at short you wont even see the trail
So you can play without having pointer issue in starcraft 2 :P
If you are using an ATI/AMD card this should fix this. I had a similar issue in the beta.
SOLUTION:
Right-click task bar
Choose Properties
Under "Preview Desktop With Aero Peak"
Deselect "Use Aero Peak To Display The Desktop"
My guess why this fixes it is the same reason we commonly see it in League of Legends and Starcraft 2 because we use the mouse to pan the camera. Once you touch the Aero peak desktop. It causes the issue on the cursor.
I figured out how to get rid of strange pointer. I run a browser when i am playing listen to pandora. when mouse mess's up alt tab and scroll on the top of browser window along the top where the [ _ window and X] buttons are and it goes back to original pointer. I dont know why it works but it does for me. before i had to restart computer to get it to change back. dumb luck i found the quick fix. I also have a ATI RADEON graphics card with the latest drivers and i even called their tech support number and talked to them they have no idea they are looking into it. alot of post i have found on google most have the ATI grahphics card that are having this problem. wierd good luck!
