There have been numerous studies on the effect of buybacks on outstanding stock price, and it is nil. It only serves to free up shares for international distribution (options, etc) without distorting either totalmo/s or eps.
Most of TLAB's cash is in various marketable securities. They apparently do not want to sell them or they will incur losses if they do. The ready cash on hand is needed for enhanced R&D and restructuring (severance costs). Companies that do poorly do not normally buyback their shares even if the price is depressed. They buyback at higher prices when they feel that the company profits will be sustained at a higher level.