Flaring on 100-400 IS L down to dust?

I recently sent a lens to be cleaned as I was getting this sort of flaring, this has been overexposed:
http://www.rhif12.co.u​k/lehmann/beforeLehman​n.jpg (eventual correct exposure was - http://www.rhif12.co.u​k …/slides/IMG_520​6water.jpg but had to heal a lot of flaring).

Having paid a premium for it to be cleaned out (I could see dust in between the elements), I tried to simulate shooting into a strong light source once it came back:

http://www.rhif12.co.u​k/lehmann/afterLehmann​.jpg

Is the flaring caused here by normal lens flare, or as a result of dust still trapped between the elements?

My 100-400 does not suffer from flare any more or less than my 24-70 or 70-200. I do make a point of always using the lens hood though.

I'd be surprised if a few specks of dust could create the problem, but theres always the possibility that theres something else wrong.

I once had a Tamron mid range zoom that was very badly repaired under warranty using a hot glue gun. Every shot after that looked like shooting through fog because light was reflecting off the shiny surface of the mess.

You shot seems to actually have the sun in shot, or very close to it. Thats always going to create problems, with any lens.

Matholwch wrote in post #7493022
I recently sent a lens to be cleaned as I was getting this sort of flaring, this has been overexposed:
http://www.rhif12.co.u​k/lehmann/beforeLehman​n.jpg (eventual correct exposure was - http://www.rhif12.co.u​k …/slides/IMG_520​6water.jpg but had to heal a lot of flaring).

Having paid a premium for it to be cleaned out (I could see dust in between the elements), I tried to simulate shooting into a strong light source once it came back:

http://www.rhif12.co.u​k/lehmann/afterLehmann​.jpg

Is the flaring caused here by normal lens flare, or as a result of dust still trapped between the elements?

If you don't mind me asking, how much did it cost you to have your 100-400 IS to be cleaned? I also have dust trapped inside and although it has not affected picture quality it does bother me.

In response to your post, I consider my lens to perform well against flare but as Lowner mentioned, aiming the lens towards bright light I'd expect that sort of performance as well. Are you using the lens hood?

Yes I am using a lens hood. As for costs, I was originally quoted £120 over the phone, but once I'd sent to them, they came back with a quote just over £140.
I paid £20 to cover the postage to them, they include the return delivery in their quote. However, I also get 6 months warranty for the work carried out. So if I see any more dust in 5 months time, I'll post it to them for another clean on the warranty.

Lowner wrote in post #7493185
My 100-400 does not suffer from flare any more or less than my 24-70 or 70-200. I do make a point of always using the lens hood though.

I'd be surprised if a few specks of dust could create the problem, but theres always the possibility that theres something else wrong.

I once had a Tamron mid range zoom that was very badly repaired under warranty using a hot glue gun. Every shot after that looked like shooting through fog because light was reflecting off the shiny surface of the mess.

You shot seems to actually have the sun in shot, or very close to it. Thats always going to create problems, with any lens.

No problems here, and the lens hood makes a lot of difference in many situations