Blizzard recently started to ban people for the use of modified Skills.txt, ANIMDATA.D2 and CHARSTATS.TXT. Also they started flagging people for the use of cGuard, which is D2BS's anti-detection.
So if you've used D2BS lately I suggest you to xfer your items off with a clean Diablo II installation. If you lost your D2 CDs you can download it from Blizzards store. McGod made a nice guide about it which you can find here.
You can expect a new cGuard release this weekend, which will contain preemptive anti-detection code aswell.