Am I able to use a 2GB SD card in my Konica Minolta Dimage G400 camera or could this cause problems.

This camera has been discontinued, and is no longer sold as new. There are still vendors that sell accessories for this camera including batteries and SD memory cards. A google search of "dimage g400 memory" reveals a number of retailers that sell SD cards of varying sizes up to 2 GB specifically for this camera.

Going beyond 2 GB however, will probably give mixed results, as most cards 4 GB (the next size up from 2 GB) are SDHC type cards. An SDHC card looks identical to the SD counterpart, but is manufactured to a different specification. The SDHC specification was developed after you camera was made, so use of cards bearing the SDHC mark is not supported.

I hope this helps!