I wouldn't think 270mA would be overdriving by any means, if it is in fact a 40 mW. I was trying to read the back of the box you have posted, is 40 mW even listed? Also, you say that the laser is currently emitting IR? Is there an IR filter present? Protect your eyes. You may have been getting 40 mW total power, with IR accounting for most.
As for it not emitting a beam anymore, the MCA and/or crystals may have been damaged with the increased power. Did you notice a burning smell or did anything get hot when running (board could be damaged)? When you turned up the pot, did it go out immediately, or did it emit a green beam, then just stop?I'm sorry to hear that this happened - it sucks.