Does anyone have a similar problem- I am seeing volumes from Yahoo! an order of magnitude larger than yesterday?

Do they match what is on the Yahoo web site?

Massive volume numbers on Yahoo! cvs

Can you give me an example? Which version of PSM are you using?

UCG.MI 1.13 08/03/2011 10:39am 0.003 1.2 1.189 1.081 587009408

Volume is absurd for 10.40 am and exceeds the total of all yesterday. Hourly total expected to be about 20-50 m

PSM Version 9.3.3 from this morning build 369

08/02/2011 15:45:000 1.16100 1.16100 1.15500 1.15500 22199328
08/02/2011 16:15:000 1.15400 1.15600 1.14700 1.14700 34380640
08/02/2011 16:45:000 1.14900 1.14900 1.14400 1.14800 52374784
08/02/2011 17:15:000 1.14000 1.14200 1.14000 1.14200 19696832
08/02/2011 17:45:000 1.14200 1.14200 1.13300 1.13300 48100352
08/02/2011 18:15:000 1.12700 1.12700 1.12700 1.12700 32629440
08/02/2011 18:45:000 1.12700 1.12700 1.12700 1.12700 0
08/03/2011 9:45:000 1.10600 1.12700 1.08400 1.10000 57800000
08/03/2011 10:15:000 1.09500 1.13600 1.09500 1.13600 48759616
08/03/2011 10:45:000 1.12500 1.13100 1.12500 1.12700 42700000
08/03/2011 11:15:000 1.14700 1.14700 1.14200 1.14200 15691968
08/03/2011 11:45:000 1.12700 1.16000 1.12700 1.14900 36000000
08/03/2011 12:15:000 1.12700 1.16200 1.12700 1.16200 65500000
08/03/2011 12:45:000 1.17000 1.18400 1.17000 1.18000 35469104
08/03/2011 13:15:000 1.18300 1.18600 1.18300 1.18600 19324544
08/03/2011 13:45:000 1.18800 1.18800 1.12700 1.18800 24400000
08/03/2011 14:15:000 1.16800 1.16800 1.16200 1.16200 38263520
08/03/2011 14:45:000 1.17000 1.17000 1.16800 1.17000 59030080
08/03/2011 15:15:000 1.16700 1.16700 1.12700 1.12700 120274112
08/03/2011 15:45:000 1.17000 1.18300 1.17000 1.17000 25312512
08/03/2011 16:15:000 1.12700 1.17000 1.12700 1.16200 225077152
08/03/2011 16:45:000 1.16000 1.16000 1.12700 1.13900 34535680
08/03/2011 17:15:000 1.12700 1.14900 1.12700 1.13800 100175040
08/03/2011 17:45:000 1.15000 1.15400 1.12700 1.15400 124226304
Open hi lo close and volume for UCG.MI over last 2 days

Take a look at the Yahoo Finance web site.

http://finance.yahoo.com/q?s=UCG.MI&ql=1

They are currently reporting a volume of 680692736, so that doesn't seem out of line to me. I can't make a judgement whether that is correct, but PSM is displaying the same number. So if Yahoo's site is reporting the volume incorrectly, you should go ahead and report it to them. Is this the only ticker for which the problem occurs?

No the problem is widespread.