Lexar 4gb sdhc memory card error

It's a lost cause. The A540 works with SD cards. While SDHC cards will fit into the slot, they are electronically incompatible and will not work in devices not designed for them. You need to stay with SD cards, 2GB and smaller.

There are several possible causes for "memory card locked", "memory card error", or "no memory card". The most common is trying to use a 4GB or higher SDHC card with an older camera made before SDHC format came out. Other causes include problems with the tiny slide switch on the side of the card, or the electrical contact switch internal to the camera. The problem may also arise from simple formatting problems if the card has never been formatted in the camera (note that this will also erase the card). Troubleshooting tips for this problem may be found at this link.

see if their might be some photos or file saved that you may have edited on the card maybe Microsoft visual studio's photo shop save to hard drive. delete with photo software and format put in camera format again. if it works with computer and not with the camera not compatible try another card

Go to this link and follow the instructions to update your camera's firmware to be compatible with High Capacity memory cards.
http://www.fujifilm.com/products/digital/download/a820_a825/fupd.html

The NV10 will not accept SDHC type memory cards. The largest card you will find it takes is a 2GB card of the SD type (not SDHC). The camera is not SDHC compliant, unfortunately. If you can return the 4GB Lexar, swap it for a 2GB of the non-SDHC variety. If this answers your question fully, please rate the solution accordingly. Thanks

First of all, the 4GB card will never be able to work in your camera. Check on its face. It likely says SDHC, and SDHC cards as this format came out after your camera was designed (I know it looks exactly like a normal SD card, but it's not).

Now the 2GB card should work with your camera as it is a standard SD card. Remove the card from your camera. Look on the side of the card for the tiny slide switch, and slide it to the other "unlocked" position. Reinsert it in the camera, and see if that corrects the problem.

you may try some card recovery software, recommended asoftech photo recovery that helped me before.
http://www.asoftech.com/apr/

If needed, you may do a quick format of the card, and then use asoftech photo recovery to recover files.

Honestly, it is most likely a defective memory card or not compatible with your camera. Sorry.

I went onto the BestBuys site and found a link for compatible memory cards - The SanDisk SDHC isn't compatible with the Canon Poswershot SD750!! Only a 2GB card will work. The Lexar SD and the Kingston Technology 2GB will.

I recently bought a DMC-TZ3 and have been researching memory cards. Several sites sell cards with the camera and list the card type. I would suggest buying one of these cards. Any cards larger than 2gb must be SDHC type SD cards. There appear to different types of SDHC cards, 1.0, 1.1 and 2.0. Check out Wikipedia.org for a description. 2.0 cards are not compatable for devices developed prior to 2.0 so that may be the reason for the camera problem. So far I haven't seen anything that states what type SDHC card the camera requires. I found a computer memory site that that sells memory that they say will work. There may be others.
http://www.mymemory.co.uk/compatible-memory/Digital_Cameras/Panasonic/Panasonic_Lumix_DMC-TZ3