Green cast on all channels

Either the lamp is on it's way out or..... the lamp is incompatible because it is not a original one. (ie the same as what they fit in the sony factory)

If your TV looks 3D, warped, or distorted it likely has a convergenge problem.
If however it just looks dull, washed out, redish, or if it looks like objects on the screen have halos the fluid in the lens has soured.
You can search google for parts or you can get the parts with repair instructions from sites such as www.TvRepairKits.com

you mean green blob? is it happening on all channels or inputs? if yes, that might be an optical block issue. call sony @ 888-993-7669.

Call Sony ASAP. They have extended the warranty on the optical block through August 31, 2010 and will replace it for free.

your power supply has failed repair/replace it

I have the same problem with my unit. I've been removing the bulb and just replace it back and unit will work again. I probably need to vacuum or check the fan out too.

2006 Model Year SXRD Televisions:
Models: KDS-50A2000, KDS-55A2000, KDS-60A2000, KDS-R60XBR2, KDS-R70XBR2
As part of the Sony commitment to quality, Sony is announcing that it is extending the limited warranty (parts and labour) in Canada on the optical block of 2006 model SXRD televisions (models listed above) until June 30, 2010 , regardless of purchase date. This extended warranty does not apply to replaceable projection lamp and other parts that may be used in the televisions.
Sony is also announcing that for any owner of these model SXRD televisions who paid out-of-pocket expenses on or before December 31, 2008 for an estimate or repair service to replace the optical block, Sony will reimburse the customer by mail for the cost of the optical block and the labour expense to replace it, subject to certain conditions. To receive reimbursement, please follow completely the directions on the claim form for reimbursement attached HERE; all claims must be postmarked by January 31, 2009. See the claim form for complete terms and conditions.
In addition, for any customer who later experiences this issue on one of the affected models, Sony will cover the cost of the optical block repair (parts and labour) at no charge through June 30, 2010.
For customers currently under a 3rd party extended warranty or service contract, please contact your third party service provider directly. This offer is available only to end-user consumers who purchased their affected television at retail in Canada and is not transferable. The offer is not available to providers, obligors, underwriters, or administrators of performance service plans, buyer protection plans, or other warranty or extended warranty programs. This offer is not part of the Sony limited warranty or Sony Care extended warranty plan.
For further details please contact Sony Canada's Customer Information Center 1-877-899-7669
All other terms of the Sony limited warranty or Sony Care extended warranty plan, as applicable, continue to apply.
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This may be due to Optical block. Click the link below to review Certain 2006 Model Year SXRD Television Extended Warranty Information - Optical Block

http://esupport.sony.com/US/perl/news-item.pl?news_id=277&mdl=KDS50A2000

New bulb

My Sony KDS 50 A2000 is 17 months old. Its the 50 Inch SXRD projection model. About two weeks ago the screen developed a green tint with cannot be tuned out, then a few days later the message began to appear on the screen that the bulb was nearing the end of its life and must be replaced.
Fortunately I have the Circuit City extended warranty.
I called and within just a few days a serviceman came out and replaced the projection bulb.
The Result: No change in the picture, the green tint remains on all channels, so I'm awating the next service call. Under the service warranty they have the option to repair or replace this set. If indeed this is the light engine (optical block) which I suspect and its going to cost $1,000 or more I may be looking at a new set.
When it works this is a great TV, but I have had three Sonys now including two other standard CRT models and now this one joins them in the junk heap, the other two also bit the dust after just about two years. Is it time to give up on Sony?
I know they have a class action suit on a similar model for this same problem. Caveat emptor