lucy24 - 8:58 pm on Feb 8, 2013 (gmt 0)
That has got to be coincidence. Especially since the whole "links to your site" area recently went bonkers, as discussed in assorted other threads.
It's hard to see how links from one isolated site could cause your own site to plummet. Unless that one site is surrounded by special google flags that say Evil Incarnate, so the merest hint of any connection will kill you. (Are there such sites? Brr.)
It probably wouldn't hurt to disavow them. With emphasis on the "probably". It's a fairly new tool.