What could cause this...?

[xAlex]

I was in a building this morning and was asked to have a quick look at a issue whereby, when the light is switched on in one room, the flourescent in the next room goes off for a second, before re-lighting as normal. This is only a recent problem apparently.
Any ideas what might cause this?
Thanks.

 

[RF Lighting]

Sounds like the installation might be on the limit for volts drop, and the inrush for the extra lamp is dropping the volts to below the limit for the fluorescent.

It could be a looped feed at the switch, and a loose screw on the common terminal

 

[xAlex]

...Your first point did cross my mind but I wondered why it had only recently manifested. I'll investigate the looped feed idea first,- sounds easier!
Thanks RF