It appears that the new WiFi card has cured the iMac of it’s won’t-stay-connected blues. The new card arrived in the mail yesterday, but since it was insured the post man conveniently left me a claim ticket so I could trek to the post office this morning on my way to kendo.
After installing the card (three minutes, a snap) and rebooting the connection has stayed all afternoon. It is nice to have the centerpiece of my multi-computer setup working properly again.
Now that I know these cards can go bad I’m thinking about getting a spare, just so if there is a next time I won’t have to live with the problem for a week waiting for the shipment.