MS Wireless Laser Mouse 5000 periodically becomes slow, jerky and unreliable

Just in the last couple of days, my mouse - a Microsoft Wireless Laser Mouse 5000 that I've owned for about a year and have until now been very happy with - has developed some strange, intermittent problems. Every so often, for no obvious reason, pointer movement becomes slow and jerky and it starts ignoring the majority of my clicks - I typically have to click the button three or four times to get it to register even a single-click. The one thing that works pretty much as expected at such times is the scroll wheel.

The problem is intermittent and unpredictable. One moment it will be as smooth as I could ask, the next it's an exercise in frustration to do the simplest tasks, then eventually the problem vanishes, as suddenly and mysteriously as it appeared. I'd say this happens about once an hour, maybe a little less, for anywhere from about 3 to about 20 minutes at a time.

I changed the batteries, then (several hours later) installed the software from Microsoft's site rather than just using the driver that comes with Win7 (the latter advice was from a similar thread from this site). Neither has helped; the problem still comes and goes as it pleases, not noticeably more or less often than before. At times when this happens, the wireless signal is (according to the aforementioned software) very good, and CPU activity is usually not particularly high, so neither of those things is the problem either.

Any ideas?