Wall Street analysis firm Bernstein downgraded Nortel stock today. It’s the fourth time firms have downgraded Nortel since March 15.

Bernstein cut its Nortel rating to market perform from outperform.

Since Nortel announced investigations of its financials and made several management changes, its stock has been downgraded by J.P. Morgan, Wachovia, and Legg Mason.

CIBC World Markets upgraded its rating for Nortel to sector outperform from sector perform on April 28.

Also Wednesday, Nortel added a new board member. He is John Manley, a former deputy prime minister in the Canadian government.

Manley held several government posts over the past 15 years, including finance minister, minister of industry, minister of foreign affairs, political minister for Ontario, and other posts.

Nortel stock traded at $3.56 in afternoon trading, up 3 cents, but nearly $5 below its $8.50 52-week high.

Nortel: www.Nortel.com