Best Buy’s woes are worsening with CEO Brian Dunn suddenly quitting overnight as it was revealed the board was investigating his personal conduct.

An initial Best Buy statement asserted there were “no disagreements” between the board and Dunn but both sides had agreed it was “time for new leadership to address the challenges that face the company”.

However a subsequent statement revealed that “certain issues were brought to the board’s attention regarding Mr. Dunn’s personal conduct, unrelated to the company’s operations or financial controls, and an audit committee investigation was initiated”.

“Prior to the completion of the investigation, Mr. Dunn chose to resign.”

Dunn has worked with Best Buy for 28 years and was appointed CEO in 2009

G. Mike Mikan has been appointed interim CEO as it searches for a permanent replacement. Mikan has been a member of Best Buy’s board of directors since 2008 and previously was CFO and executive VP of health insurer UnitedHealth Group.

Best Buy is facing serious challenges, recording a $1.2 billion loss for the last fiscal year. It followed that up by revealing plans to close 50 stores, axe 400 jobs and cut $800 million in overheads.

It failed in ambitious moves to roll out its large format stores in Great Britain and China and in its US home market and it is struggling to maintain viability of its Big Box formats as an increasing number of consumers shop online and the DVD and music software market continues to decline.

Bright spots are ongoing growth in a Chinese domestic retail chain it purchased outright and in US online sales which grew nearly 20 per cent last year to $2.95 billion.