I have just had mine done, now running V1.10.030.
If anyone is having difficulties with their N91's with corrupt data on HDD, or apps not working properly, or just general unreliability, get the software upgraded. Mine is much better now, originally on Vodafone, now unlocked and with generic software (latest i believe).
I have more phone mem available and it's not missed a beat in 3 days, which is a record so far.
Typical Nokia thing, I had the same with the 6630, which was one of the first 12 available in the country. Unreliable, once upgraded it was superb, and still is....