Also their growth is down.
Your friendly neighborhood tax agency is a special case of firm, which can commit to paying you money in the future. One way they can do this is, when you lose money in year N, they can let you carry that loss forward for up to X years, so that when you're taxed on your income in year N+3 you might be able to offset some of that income with the loss you made years earlier, reducing the amount of tax you incur.
The guesstimated value of that offset in taxes is your tax asset. If your marginal rate is 30%, and you can offset $1 million in revenue, the implied value is +/- $300k. Importantly, if you guesstimate poorly or your friendly local tax agency decides to change rules on you in the interim, you have to adjust the value on your balance sheet. This can be problematic if the tax asset is a material portion of your notional value.
If you've got, oh, $300 million in cash ($200 million in remaining investment plus we'll say $100 million in collected revenue) and another $25 million in accounts receivable then the tax asset is worth about, round numbers, $250 million, or 43% of the book value of the company.
Having to write down 43% of your book value would suck.
This is, again, not outlandish for a company on that trajectory. If the revenue is growing rapidly and forecast to continue growing rapidly the company is in a wonderful spot.
For example, companies will calculate depreciation on their capital assets using various methods. However the IRS/CRA have their own methods for calculating depreciation on these assets. The difference between these two amounts can create a deferred income tax liability or asset. That is, if you record depreciation higher than what the IRS calculates as, the income tax expense you record on your income statement will be higher than the amount you are actually charged.
There are also rules which identify whether or not companies can put a deferred tax asset on their balance sheet. Under International Accounting Standards (IFRS), companies must establish that they can realize these assets by having sufficient income to apply them against in the future. In the U.S., as was the case here, a valuation allowance was applied to decrease the asset as they indicated that they weren't likely going to have a sufficient net income in future periods to apply that asset to tax expenses.
Anyways I'm a bit rough on it as while I've got an education in accounting it's not my day-to-day job anymore. Additionally I'm not that familiar with U.S. accounting standards
I am not an accountant, here's a likely better explanation: http://www.investopedia.com/terms/d/deferredtaxasset.asp