I'm experiencing exactly the same problem as you described here.
I have a 3ware/amcc 9550sx-8lp controller with eight 300GB Maxline III harddisks (7V300F0). They were equiped with firmware VA111630 and produced near the end of Jan 2006. The system is a Supermicro SC833T-R760 chassis (with 760W PSU), and I'm running Linux, 64-bit, but I don't think this is a OS related problem.
The system works fine, but randomly with intervals of many days of normal operation q drive drops out of the array. It is always a different drive, and always a different slot. Rebooting the machine does not help. The drive remains completely dead or inaccessible. I have to cold boot the machine, or I have to hot-remove and reinsert the drive. Then it starts working again completely normally.
I complained about this to AMCC and Maxtor, and they sent me firmware VA111670. The problem did not go away, although I have the impression that the frequency of occurance has been reduced somewhat.
I have tried all sorts of things, like reducing the speed from 3.0Gbps to 1.5Gbps, all to no avail. The longest period of continuous trouble free operation was 17 days in a row. The shortest 22 hours. On average statistically each drive fails every 56 days of operation (/8 drives = 1 case every week on average).
The "defective" drives afterwards do not appear to have any sector defects that might cause these timeouts.
I'm putting my story here in the hope that there are other "me too"'s. Maxtor claims to have only received one report about this, namely mine. I have told them that I am not the only one, but for "only two" customers they are refusing to escalate this problem with a high priority. In the meantime I have been experiencing this problem for 8 weeks now. "Complete customer satisfaction". I'm not satisfied at all at this moment.
I know that AMCC/3ware, the RAID card manufacturer, is currently in the process of attempting to reproduce this problem themselves with the Maxtor hard drives. I'm waiting for their feedback.