Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

The stock market posted modest losses today, but they still didn't prevent a solid positive return for the month, with the S&P 500 picking up more than 4% in October. But today was a lot worse for Sony (NYSE:SNE), Sequenom (NASDAQ: SQNM), and Ariad Pharmaceuticals (NASDAQ: ARIA), all of which had some devastating losses. Let's take a closer look to find out what sent those three stocks crashing downward today.

Sony lost 11% of its value as the Japanese entertainment and electronics giant reported a net loss for the quarter and reduced its full-year earnings guidance. Results from the company's television unit were particularly disappointing, as the TV division failed to repeat the favorable results it achieved in its June quarter and posted losses of almost $100 million. With losses in Sony's entertainment division also weighing on overall results and with the company falling behind rivals Samsung and Apple in the consumer electronics and smartphone space, Sony will need to rely on the PlayStation 4's release to help bolster its flagging results.

Sequenom dropped almost 23% after a federal court invalidated a key patent in its infringement lawsuit against a small privately held company. The court granted Ariosa Diagnostics summary judgment in the suit, declaring that Sequenom's patent was invalid because the subject of the patent wasn't eligible for patent protection in the first place. Sequenom intends to appeal, but given the importance of the prenatal genetic testing that relies on the patent, investors fear that the order could open up the industry to new competition. Moreover, as Fool contributor Sean Williams pointed out earlier today, Sequenom had hoped to see a judgment against Ariosa bring some extra cash into its coffers.

Ariad Pharmaceuticals was the big decliner of the day, crashing 44% as the Food and Drug Administration asked the biopharmaceutical company to stop selling its Iclusig blood-cancer drug. The news follows negative findings from earlier in the month that found a substantial elevation in the incidence of arterial blood clots for Iclusig patients, which resulted in a clinical hold for the drug's ongoing trials and later led Ariad to halt its EPIC study for chronic myeloid leukemia. As bad as it sounds, the news doesn't mean certain failure for Ariad's future, but investors will have to deal with uncertainty until the FDA takes a closer look at Iclusig.