USB connected 'phone affecting start up?

Hi people.

I have an Acer Veriton PC running W7 Pro.
Have had a couple of EXTREMELY slow start ups recently, with the black ACER screen coming up and
staying there for ages, and the fans running very fast.

I've recently blown all the dust out of the cabinet, so that's not the issue AFAIK.

Is it possible that USB connected 'phones could be affecting proper start up?
I've had problems before if there are CD's in the drive, would a 'phone cause the same sort of problem?

The Missus left hers connected, and after I disconnected and restarted, no problem.

Coincidence, or cure?

Many thanks. Tony.