An article in today's Wall Street Journal (2015-08-16) titled A New Computer Glitch is Rocking the Mutual Fund Industry is all about how some kind of computer (software?) failure at a company called SunGard Data Systems Inc. is impacting large mutual fund and ETF companies in that they're unable to accurately value their funds (compute the net asset value).
Several traders said they were forced to calculate their own net asset value for ETFs and that they widened the spreads, or the difference, between listed buying and selling prices to accommodate for the higher risk of trading.
So, putting aside ETFs for the moment (perhaps they need valuations during the day) a mutual fund's valuation is published once per day, at close of market.
Given that a mutual fund manager knows, at the end of the day, precisely how many shares/units/whatever of each investment (stock, equity, etc.) they own, plus their bank balance, what is there about exactly computing a mutual fund's value that can't be done with a query against finance.yahoo.com and a very simple Excel spreadsheet?