Several TiVo owners have recently contacted CNET News.com to complain of a "stuttering" problem with their recorders that caused video to freeze repeatedly, eventually leading to a system crash.
According to some, the problem started soon after the TiVo software was upgraded in the past few weeks.
A TiVo spokeswoman blamed the problems on routine hard drive glitches, however. "The hard drive failures have been within the normal rates of industry hard drive failures," said TiVo spokeswoman Rebecca Baer. "At this point, there is no reason to believe that it is connected to the software."
Baer could not specify the number of complaints or overall failure rates.
Jim Porter, president of hard drive research firm Disk/Trend, said the drives used in consumer electronics products are designed to last about 300,000 hours, or for about 35 years of continuous use. Porter added that one out of 34 drives on average is expected to fail within the first year.
TiVo's service was introduced in January 1999.
Last month TiVo began installing version 2.01 of its software. The upgrade is automatically uploaded to TiVo boxes along with the TV programming information that is routinely delivered through a phone line.
Some subscribers have posted complaints to Web forums blaming the stuttering problem on the recent upgrade.
According to subscriber Kevin Potterfield, "The video and audio briefly freezes...The intervals that the shows would freeze up got more frequent until the whole system locked up. This didn't start happening until the day I got the upgrade."
The new software includes features such as WishLists, which allow subscribers to program TiVo to search for shows with certain actors, directors or keywords and to automatically record the programs.
Digital video recorders are similar to VCRs, allowing subscribers to record programming to a hard drive instead of to a VHS tape. TiVo's service learns the type of shows subscribers enjoy based on their previous programming choices and records those programs.
Sony and Philips Electronics manufacture set-top boxes that support TiVo's service, and Quantum is among the hard drive manufacturers.
Last month, some subscribers to DirecTV's satellite TV service using TiVo and Microsoft's UltimateTV service were hit with software bugs.