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Simple to disable it, just take the mod out. The worlds should stay there if you ever want to add it back in, as they're stored in the world's save folder.
If you provide a console log and crash report, we can try to fix the problem.
Right now there is a Bug in Buildcraft which causes Minecraft to crash if two Item Tesseracts that are linked feed into each other with one buildcraft pipe inbetween. This will corrupt your save until you change the Tesseract ID and therefore delete the block.