My Mac repeatedly closes and restarts and Sophos is being blamed.

Is there a virus that has target Sophos.

I use OS 10.9.3 and I have been using Sophos 9.x for quite sometime.  Today my compter shut doewn and restarted a number of times.  I nted in the report that Sophos was noted in a panic close (see below).  Thge i get a notice out of nowhere (see below) as if from Apple, but not sure.  I deleted Sophos frm the system and reinstalled it.  Not only did the problem occur again, but my preferernces were affceted.  Also, I notcie thatone of my two back up derives is ejected for no reason. 

I ran Sophos at one point and not htreats wewre detetected, but it noted "issues detected" without explination.

What is going on?

Thu Jun 26 17:15:28 2014

panic(cpu 1 caller 0xffffff80101db160): "vnode_rele_ext: vp 0xffffff8035e55870 usecount -ve : -1.  v_tag = 16, v_type = 1, v_flag = 84800."@/SourceCache/xnu/xnu-2422.100.13/bsd/vfs/vfs_subr.c:1788

Backtrace (CPU 1), Frame : Return Address

0xffffff811dfa35d0 : 0xffffff8010022fa9

0xffffff811dfa3650 : 0xffffff80101db160

0xffffff811dfa3690 : 0xffffff7f905c2762

0xffffff811dfa36b0 : 0xffffff7f905c1f54

0xffffff811dfa39e0 : 0xffffff7f905c3eb3

0xffffff811dfa3a20 : 0xffffff80103b5ca1

0xffffff811dfa3a80 : 0xffffff80101e003d

0xffffff811dfa3ad0 : 0xffffff80101f4bc0

0xffffff811dfa3b70 : 0xffffff80101e6745

0xffffff811dfa3c20 : 0xffffff80101e7002

0xffffff811dfa3f50 : 0xffffff8010440653

0xffffff811dfa3fb0 : 0xffffff80100f3c56

      Kernel Extensions in backtrace:

         com.sophos.kext.sav(9.0.61)[00000000-0000-0000-0000-000000000000]@0xffffff7f905c1000->0xffffff7f905c5fff

BSD process name corresponding to current thread: mds_stores

Mac OS version:

13D65

Kernel version:

Darwin Kernel Version 13.2.0: Thu Apr 17 23:03:13 PDT 2014; root:xnu-2422.100.13~1/RELEASE_X86_64

Kernel UUID: ADD73AE6-88B0-32FB-A8BB-4F7C8BE4092E

Kernel slide:     0x000000000fe00000

Kernel text base: 0xffffff8010000000

System model name: iMac13,2 (Mac-FC02E91DDD3FA6A4)

System uptime in nanoseconds: 352043741723

last loaded kext at 172000146885: com.sony.driver.dsccamFirmwareUpdaterType00        1 (addr 0xffffff7f924cf000, size 49152)

last unloaded kext at 148808186566: com.apple.driver.AppleFileSystemDriver      3.0.1 (addr 0xffffff7f923d9000, size 8192)

loaded kexts:

com.sony.driver.dsccamFirmwareUpdaterType00    1

com.sophos.kext.sav   9.0.61

com.sophos.nke.swi   9.0.53

com.apple.driver.AppleFireWireStorage        3.4.1