I don't think so; rather, I believe it's from either a badly-written spider, or a bot trying to "fingerprint" web servers and operating systems. There was a spider going around a week or two ago asking for /a/non/existant/file.png, apparently trying really, really hard to generate 404 errors. There was also a spider running around for the longest time that didn't parse subdirectories correctly, and wound up making requests like "GET /directory%0;file.html" over and over and over again... It's just something that happens.
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the other thing that makes me wonder is that the IP addresses that make the requests are at random and at times, rampant. i was able to extract a list of the addresses and it looks like there's at least 100-125 variations, some are from the same ip block, others are just from the typical providers like comcast and pacbell.