Blank IR film

Rereading all of the posts, I too believe it could well be the IR filter giving you problems.

I buy a lot of cheapie bits that aren't too important on ebay etc. but for filters of all types it's worth buying a branded version in your home country, so that if there are any problems you can take them back. Rereading again, I see that you say that you used a branded filter, ('I use an IR filter something like Hoya R72, ISO 06') but was it bought at home or via ebay abroad? I'm just trying to whittle down the possibilities to solve your problem.

Terry S

Bob:
I have a 49mm 720nm filter that I have used successfully with the Rollei IR film on my C330.
And I have a 46mm - 49mm step-up ring.
We should get together and do a test - half roll with one filter, and half roll with the other.