Over about eight seconds immediately before the Reserve Bank announced its decision to cut its cash rate on February 3, the Australian dollar fell by about 40 basis points (50 basis points is a half a percentage point), and climbed by the same amount.

The announcement that the central bank had decided to cut its cash rate from 2.5 per cent to 2.25 per cent surprised many in the markets when it came, and the dollar fell again. It is possible that those who sold seconds ahead of the news made money.

The choice for the Reserve on that day was to either hold its cash rate, or cut it. In the absence of insider knowledge, an investor's odds on getting the call right were one in two.

The choice on Tuesday this week for the Reserve was again binary – to cut again, or to hold: raising the cash rate was not an option.

Many in the markets ignored a hint in the minutes of the February 3 meeting that the bank's board had discussed cutting in February OR March but not both, and there was some degree of rate-cut pricing in the dollar as the 2.30pm deadline for the announcement of the March decision approached.

About 40 seconds before the decision became public, the dollar moved up by about a half a percentage point. Three-year Commonwealth bond prices also fell. This time there was no last-second reversal, and the price moves were once again prescient. The decision was to leave the cash rate at 2.25 per cent, news that pushed the dollar up, and share and bond prices down.

In the absence of insider knowledge, the odds on guessing what the Reserve would do on Tuesday were once again one in two. The chances of guessing right on February 3 and again on March 3 were one in four, however: unlikely enough to persuade the Reserve to pick up the phone on Tuesday, and get ASIC's market surveillance unit involved.

Suggestions that the Reserve was hacked can be clouted to the boundary. The Reserve's firewalls have never been breached, and its interest rate decision statement is held on an internal IT platform before it is released.

There is a computerised record of when it is placed on the Reserve's website and released to news agencies, and it confirms that the news did not get out prematurely.

A leak is another possibility, and it cannot yet be discounted. As one market player put it to me on Wednesday, if it looks like a duck, walks like a duck and quacks like a duck, maybe it is a duck.

Rate decisions are only known by a small group of Reserve insiders ahead of their release, and a leak if it did occur is highly likely to have been inadvertent.

It would still be a major embarrassment for the Reserve, however. Market participants have already been startled this year by the central bank's shift from last year's statements that rates were in a "period of stability" to a rate cut in February, and what turned out to be accurate media predictions that preceded the rate cut.

It is also possible that the spike was similar to recent unusual price action in overseas markets ahead of important announcements.

Regulatory action since the global crisis has thinned the ranks of active foreign exchange dealers, and reduced the amount of money they commit to the market.

Regulatory probes of currency market price fixing have also sidelined seasoned forex dealers around the world, and investors are also divided right now about whether the market is a bubble about to burst, or headed higher.

All of this is working to create unusually low liquidity and unusually wide buy-sell spreads ahead of market-sensitive announcements, about interest rates, and also about economic data.

Australian dollar buy-sell spreads in the run-in to Tuesday's announcement were about 40 basis points, wide enough to give trades extra potential to spark big price movements. They could then also have been magnified by computerised high-frequency "momentum trades" that essentially locate a price trend, and join it.

ASIC is the organisation charged with getting to the bottom of it all, firstly by locating the trade that was the catalyst, and tracing it back to its origin. The Reserve will be hoping that the trail does not lead somewhere that damages its reputation.