InvalidOperationException - object is currently in use elsewhere

I've gone through this SO question but it didn't help.

The case here is different. I'm using Backgroundworkers. 1st backgroundworker starts operating on the image input of user and inside firstbackgroundworker_runworkercompleted() I'm using calling 3 other backgroundworkers

 algo1backgroundworker.RunWorkerAsync();
 algo2backgroundworker.RunWorkerAsync();
 algo3backgroundworker.RunWorkerAsync();

this is the code for each:

algo1backgroundworker_DoWork()
{
 Image img = this.picturebox.Image;
 imgclone = img.clone();
 //operate on imgclone and output it
}

algo2backgroundworker_DoWork()
{
 Image img = this.picturebox.Image;
 imgclone = img.clone();
 //operate on imgclone and output it
}

similar operations are done in other algo*backgrougrondworker_doWork().

Now SOMETIMES I'm getting "InvalidOperationException - object is currently in use elsewhere". Its very arbitrary. I somtimes get this in algo1backgroundworker_DoWork and sometimes in algo2backgroundworker_DoWork and sometimes in Application.Run(new myWindowsForm());

I've no clue about whats happening.