this has been happening with weapons brought in from classic. Once you have this issue start, then it going to be hard to get rid of. 2 other user are experiencing this also. Dont know how to fix it permanent yet.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit