Funny (not good) noises - #1 Wheezy sound from a/c

[carlsun]

1999 V70XC, 123,000 miles
Air conditioning system makes a wheezy flute-like sound frequently when starting and turning off car. I had the engine coolant radiator replaced last year. Prior to that the a/c cooled very well and no sounds. All last summer (2009) car struggled to keep cabin comfortable in the summer. Flute sounds began then too. This spring, I replenshed the r134 (I had not checked it last year and dumba-- garage I took it to on two occasions last year apparently did not check it either). Still have had the flute sounds, but air stayed strong all summer, even when temps were over 100 for 23 of 26 days in July and August.

Thoughts? Opinions?