Why does my SD data get messed up when i connect to PC with USB? Every time I connect my phone to my computer via USB (Huawei U8666E, Android 4.0.3) even after I've disconnected my phone, the following 2 things happen (that I can tell): My ringtone goes back to "Default" (i'm using a custom one which is saved on the SD memory) and my music playlist (the only one i have) goes empty. No music file is missing, they're just removed from the playlist, and they, too, are on my SD memory.

What can i do to fix or circumvent the issue?

Edit: The problem is not that it happens while the phone is hooked on the computer, but that it persists AFTER i disconnect it. In other words, after disconnecting the phone, i have to manually rebuild my playlists and change the ringtone again. Is there a way for me to transfer data between PC and phone without having to "reconfigure" the phone after the process? Or better yet a way to use the USB normally without the "reconfiguring" having to take place?
It sounds like your ROM doesn't properly reset settings when the sdcard is re-enabled (since it obviously becomes unavailable to the OS when using USB Mass Storage). Unfortunately, this is likely an issue with your ROM and I don't think there is a likely setting that would fix it.

However, in Android 3.0, Google added MTP (Media Transfer Protocol) support and it has been in all versions since. This allows the sdcard to remain mounted in the Android system while also allowing it to be accessed on the computer. I can't remember the exact layout of ICS, but to be able to change it to MTP from UMS, it is probably pretty close to Settings -&gt; Storage -&gt; Menu -&gt; USB Computer Connection -&gt; enable MTP