"Longtime VC investor bails just one month before battery maker's bankruptcy filing." ($AONE)

I wonder why this A123 investor held on for so long?

"[When] A123 went public in September 2009[,] North Bridge held a 9% equity position [which] was valued at nearly $120 million at the time of IPO, and $228 million just a few days later.

Over the intervening three years, North Bridge didn't sell a single share. Not when lockups originally expired. Not when the stock price steadily declined. Not when it was forced to recall defective electric car batteries last December. Not when the company signed a $465 million bail-out of sorts in early August with Chinese auto parts maker Wanxiang Group. Not a few days later when U.S. Congressmen began objecting to the deal, or when NASDAQ issue[d] a delisting notice on August 22 [...] No, North Bridge didn't unload its first share until August 28..."