random output with sub(fixed = TRUE)

I've noticed what I think is curious behavior in using 'sub(fixed = TRUE)' and 
was wondering if my expectation is incorrect.  Here is one example:

v <- paste(0:10, "asdf", sep = ".")
sub(".asdf", "", v, fixed = TRUE)

The results I get are

 > sub(".asdf", "", v, fixed = TRUE)

  [1] "0"               "1\0st\0\0"       "2\0<af>\001\0\0" "3\0<af>\001\0\0"
  [5] "4\0mes\0"        "5\0<ba>\001\0\0" "6\0\0\0\0\0"     "7\0\0\0m\0"
  [9] "8\0\0\0t\0"      "9\0<fe>\0\0\0"   "10\0\0\0\0\0"

 >

I expected "0" in the first entry and everything else would be unchanged.  Your 
results may vary since every time I run 'sub()' in this way, I get a slightly 
different answer in entires 2 through 11.

As it turns out, 'gsub(fixed = TRUE)' gives me the answer I *actually* wanted, 
which was to replace the string in every entry.  But I still think the behavior 
of 'sub(fixed = TRUE) is a bit odd.

 > version

          _
platform x86_64-unknown-linux-gnu
arch     x86_64
os       linux-gnu
system   x86_64, linux-gnu
status
major    2
minor    2.1
year     2005
month    12
day      20
svn rev  36812
language R

 >