"session hijack detected"

I got an interesting error when G2 was generating thumbnails. Basically, I just opened an album on localhost that didn't have albums and I got the following in the log:

2005-01-15 07:48:08 [a3f78ae186382a9289cd3696130ae083] Executing: cmd /c " 
"E:\apps\ImageMagick-6.1.7\convert"  "-quality"  "95"  "-size"  "150x150"  "-geometry"  
"150x150"  "-strip"  "E:\home\g2data\albums\galka\Mammoth2004\IMG_1703.jpg"  
"E:\home\g2data\tmp\img318.tmp"  2> "E:\home\g2data\tmp\g2d319.tmp" "
2005-01-15 07:48:08 [a3f78ae186382a9289cd3696130ae083] Lock id 6 was left hanging!
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] clearstatcache()
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] 
filesize(E:\home\g2data\sessions\a3f78ae186382a9289cd3696130ae083)
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] clearstatcache()
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] 
filesize(E:\home\g2data\sessions\a3f78ae186382a9289cd3696130ae083)
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] Session hijack detected: saved vs. 
current below
2005-01-15 07:48:41 [a3f78ae186382a9289cd3696130ae083] Array
(
    [0] => 127.0.0.1
    [1] => 88b346914c1b897a340666314922ad04
)

At which time Apache generated a dump.

I can't reproduce the problem; so it's more like - if anybody runs into something similar and can help troubleshoot the problem - it would be great!