I believe this is the main reason for the sell off on heavy volume that has been occurring, brining the stock down to 5-month lows.
Even though most are blaming it on the IPO of BigBand Networks (BBND), BigBand is not a competitor of Riverbed, and next quarter is looking to be very strong. RVBD has already taken a quick snap back after the selling was complete, and I believe this stock will go much higher in anticipation for another strong earnings report.
Disclosure: Author has a long position in RVBD
RVBD 1-yr chart