Hi all!
I'm having some problems with the transparency because GIMP changes slightly bright pink pixels when they are near other color. Searching the forums I discovered that I have to remove anti-aliasing to fix it, but... I don't know how to do it!
How can I remove anti-aliasing with Gimp? And, is there any better way to fix this problem without removing anti-aliasing?

Thanks,
suPERLman

In GIMP, use the N instead of the P tool - and use a brush with no alpha. That way, it shouldn't do any anti-aliasing. For other tools, there are also settings to avoid anti aliasing. E.g. the F tool, just uncheck the "Anti Aliasing" checkbox.