1, Since whatever project we are connecting to Comm port by using MAX323, If its ground pin (i.e. third wire along with RXD and TXD) is not broken with computer. Then is it safe.

2, Few months ago, I have connected my PC through a Lan Card with my neighbours PC, After running few hours my side of lan card becomes dead. I have connected it through 4-line hub. Then we check the system with with 8-line hub and 2 more lan card, but the result was 3 dead lan cards. Since each of these lan cards are isolated with built in transformers, why this problem is happening. Does connecting ground (body) of PCs will help.

3, By use transformers or Opto-couplers, can we make sure that Comm ports are absolutely save.