DVD plyer/Burner refuses to read commercial disc and keeps ejecting, DVD plyer/Burner refuses to read commercial disc and keeps ejecting

For a few weeks I've noticed my internal dvd drive won't burn CDs etc, keeps producing various errors, and today it keeps ejecting commercially bought dvd's ( music concerts ).

I can play them thru an external DVD player/Burner and they mount on the desktop and play in DVD player.

I've tried re-setting the SMC.

In System Prefs. it shows OK and if a disc is inserted and what speeds, whether its burnable or not.

My Protection plan expired end of Dec!!!

I had the HDD replaced in Nov under Apple's replacement programme - could it have become disconnected then?

Just put in a Blank CD and it mounts on the d/top and shows up in system prefs as;

OPTIARC DVD RW AD-5680H:

Firmware Revision: 3AHB

Interconnect: ATAPI

Burn Support: Yes (Apple Shipping Drive)

Cache: 2048 KB

Reads DVD: Yes

CD-Write: -R, -RW

DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW

Write Strategies: CD-TAO, CD-SAO, CD-Raw, DVD-DAO

Media:

Type: CD-R

Blank: Yes

Erasable: No

Overwritable: Yes

Appendable: Yes

Write Speeds: 8x, 16x, 24x

Also just tried with a commercially made music CD and it also is listed here;

OPTIARC DVD RW AD-5680H:

Firmware Revision: 3AHB

Interconnect: ATAPI

Burn Support: Yes (Apple Shipping Drive)

Cache: 2048 KB

Reads DVD: Yes

CD-Write: -R, -RW

DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW

Write Strategies: CD-TAO, CD-SAO, CD-Raw, DVD-DAO

Media:

Type: CD-ROM

Blank: No

Erasable: No

Overwritable: No

Appendable: No

However, I just tried with 5 other DVD/CDs and each one was not recognised and efected automaically.

Can anyone help as to what the problem is?