In February I bough a set of brass/copper fuses like the one you describe from an ebay seller called "fastvw99", but didn't get yet a chance to replace my old aluminum ones. I really don't have any reason to suspect that mine could also be bad ones, but I'll keep an eye on them for any problems like it happened to you, and just in case will definitively not change them out all at once like I had planned.
In any case the same seller is still offering them as item # 300213444711
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=300213444711
Do these look like yours?
BTW, how did you test for electrical losses on the new fuses? did you measure the voltage across the fuse while current draw was flowing through it?