QI'm contemplating getting the new G5 iMac, but I have heard whispers about a "midplane" problem affecting the electrical wiring. Is this a real problem?

AWhen I reviewed the iMac G5 last September, I didn't experience any reliability issues. Since then, however, I have seen enough secondhand reports about wiring defects to suspect something is amiss, at least in the first version of this model. (Apple updated the iMac G5 in early May.)

Apple did not answer questions about this issue. But one of the oldest and best Mac-news sites, MacInTouch, recently conducted its own survey: Of 4,508 readers who reported buying an original iMac G5, almost 23 percent had experienced failures (www.macintouch.com/reliability). Owners of first-version iMac G5s with 20-inch screens had the worst results, with a 31 percent failure rate.

Owners of the newest model, however, did far better: Of 1,401 buyers, 11.5 percent reported failures, a figure in line with the repair-history figures in Consumer Reports' June 2005 survey of computer buyers.

I do not plan to run Internet Explorer, but I understand that some programs will use this browser anyway. Would I be safer if I disable ActiveX?

Yes, but it's not terribly practical to do so. Of the sites that require you to run IE, many -- including Microsoft's Windows Update page -- employ ActiveX, an easily abused Microsoft technology that lets Web sites run programs right on your computer. And switching ActiveX on, then off, is a convoluted process. If you minimize your use of IE and ensure that other people who use your computer don't run it (it helps to get rid of any desktop shortcuts to Microsoft's browser), you should be safe enough.

-- Rob Pegoraro

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or rob@twp.com.