Had my alternator belt replaced at the dealer 2 weeks ago (86K). After 1 week, it started squealing more and more everyday. I do not know if the dealer didn't put enough tension, but it was pretty loose. I tightened the belt and it fixed the problem.
If your belts are old and worn, replace them. I heard the best belts are Goodyear Gatorbacks. They fixed a lot of squealing problems for a lot of people. I just purchased the belts from summitracing at a very good price.
GTR-40228 is the timing belt for $30.39
GTR-4040360 is the alternator belt for $9.99
GTR-4050457 is the PS and AC belt for $11.69
http://www.goodyearbeltsandhose.ca/replacement/selector.html
<table bgcolor="#ffffff" border="1" cellpadding="1" cellspacing="0" width="735"><tbody><tr><td colspan="5" align="left" valign="top">[FONT=arial,helvetica,geneva,sans-serif]
Poly-V Belts[/FONT]</td> </tr> <tr> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
4040360[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
Poly-V, Alt[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
4PK0915[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> </tr> <tr> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
4050405[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
Poly-V, PS w/o AC[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
5PK1030[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> </tr> <tr> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
4050457[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
Poly-V, PS & AC[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
5PK1160[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td> </tr> <tr> <td colspan="5" align="left" valign="top">[FONT=arial,helvetica,geneva,sans-serif]
Timing Belts[/FONT]</td> </tr> <tr> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
40228[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
Timing Belt[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif]
Interference Engine Application[/FONT]</td> <td align="left">[FONT=arial,helvetica,geneva,sans-serif] [/FONT]</td></tr></tbody></table>