LONDON -- Yesterday's downgrade of 15 banks put the FTSE 100 (INDEX: ^FTSE) into reverse today, with the London index of top shares falling 50 points, or 1%, in early trading. Royal Bank of Scotland, Barclays, HSBC Holdings, and Lloyds Banking Group were all marked down by the credit rating agency.

Other companies lost heavily during the week, too, as a result of their own individual news. We look at three from various FTSE indexes that suffered this week.

Drilling halted
Max Petroleum (LSE: MXP.L) saw a mammoth 56% slashed off its shares, which fell 4.9 pence to 4 pence after announcing drilling problems in Kazakhstan. For the second time, exploration of its NUR-1 well has been halted after drilling equipment became stuck in a salt layer. In April, it got stuck at 5,718 meters, but after a second attempt, apparently using higher-density mud, it only reached 5,722 meters.

This further delay is creating financial problems, and the firm is now forced to seek additional capital from lenders and equity financiers in order to finish the job.

Mining slump
Natural resources in general had a bad week, with Xstrata (LSE: XTA.L) one the biggest fallers among the FTSE 100 miners, down 8% to 820 pence. Fears of a hard landing for the previously soaring Chinese economy are relentlessly pushing down the prices of minerals, and shares in the companies that dig them up have gone down with them.

At the current price, Xstrata shares are on a forward price-to-earnings ratio of just 9.5, even if we use the most pessimistic recent earnings forecasts. Are the big miners unfairly depressed now? They just might be.

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Unconventional fundraising
Severn Trent (LSE: SVT.L) has lost 7.5% on the week, falling 130 pence to 1,606 pence. The reason appears to be the water supplier's unusual method of raising the rest of the 2.5 billion pounds needed for its 2010 to 2015 capital investment program.

It is launching an inflation-linked 10-year retail bond, aimed at private investors, with an interest rate of 1.3% per year above the UK Retail Prices Index. The bond issue is expected to raise up to 100 million pounds. Do you fancy some? There's a minimum investment of just 2,000 pounds. If not, maybe it's an opportunity to snap up a good dividend-payer at a cheaper price.

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