If you got an physical machine in 800pgs/min && your VM image is a perfect copy of your physical one, then the only difference seem here is your VM.

Are you on Windows though? Windows limits you can only have a few live network connection at a time ( 4 as far as I can remember in XP decade, and 20 max if you have a win7 pro, after some reg hack ), thus you may experience broken result which caused those complains. Consider vm-to-windows consumed 1 channel, and windows-to-web consumed 1 channel, and so forth times 2 network loading( not precisely like that, but the concept is sort of like this). If a round trip is not done fast enough, the afterwards queries are all jammed.

Maybe you can check your scraper how many threads, forks are run at a same time