I just bought this on Steam for the Summer Sale and have been suffering this exact problem. My framerate is slowed down and my mouse stutters, I wasn't even able to type in the bug report because it would not register the keystrokes and to even open the bug reporter I had to hold down my right mouse button until it recognized what I was doing. The music in the background is completely fine though.
COMPUTER SPECS:
Windows 7 64-bit Home Edition
ATI Mobility RADEON HD 4650
6 GB of RAM
Dell Laptop
Laptop's built in mouse pad/ Microsoft Wireless Mobile Mouse 6000
I have tried all of these solutions and here are their results:
SOLUTION 1: Power down your computer, restart it, then re-run Atom Zombie Smasher.
EFFECT: No difference.
SOLUTION 2: If you have a joystick/gamepad, try plugging it in before starting the game.
EFFECT: No difference. (Probably because of the built in mouse pad of my laptop, but even disabling that did nothing.)
SOLUTION 3: if that does not work, go to your Atom Zombie Smasher's "data" folder (likely c:\program files (x86)\atom zombie smasher\data) and delete the ATIGTKXX.dll file.
EFFECT: No difference.
SOLUTION 4: If that does not work, go to your Atom Zombie Smasher's "data" folder (likely c:\program files (x86)\atom zombie smasher\data) and delete the OPENAL32.dll file.
EFFECT: Crashed the game completely, not even letting it load. (Sent the report when Blendo's crash reporter popped up)
SOLUTION 5: If all that fails, copy & replace these libraries into your "atom zombie smasher\data" folder:
http://blendogames.com/dev/sfml17lib.zipEFFECT: No difference.
SOLUTION 6: 1. Reinstall the C++ redistributable
EFFECT: No difference.
SOLUTION 7: Reinstall the .Net framework
EFFECT: No difference.
SOLUTION 8: Verifying game cache.
EFFECT: No difference.
SOLUTION 9: Updating graphics card
EFFECT: No difference.
SOLUTION 10: Reinstalling the OpenAL library and running the game
EFFECT: No difference
SOLUTION 11: Running with a difference mouse
EFFECT: No difference.
WINDOW TEST: Download
http://blendogames.com/dev/windowtest04.zip and report the numbers it displays when mouse moves.
REPORT: FPS 717 - Mouse Events: 125
SOLUTION 12: Running the game with headphone jacks plugged in
EFFECT: No difference.
SOLUTION 13: Try on another computer.
EFFECT: It works perfectly fine on my outdated desktop which has these specs
Windows Vista 32-bit Home Edition
NVIDIA GeForce 8600 GT (Not updated)
3 GB of RAM
HP Desktop
USB Wired Mouse (That created no difference when plugged into my laptop.)
Even though it works fine on my desktop I really hope a patch will be made to solve this issue soon. I rather play this on my Laptop for the mobility, especially when taking it to friends' places to play the local co-op.