Index with duplicate values

Hi. We have a table that has 2,500,000 rows. We added an index on a column that only has a handful of values: say for example: "ABC" - 2,499,000 rows "DEF" - 200 rows "GHI" - 200 rows "JKL" - 200 rows "MNO" - 200 rows "PQR" - 200 rows I am suspicious that this may cause problems: 1) With a 4K page size it seems that I'll get around 585 rows per page in the index. For the "ABC" column I think I'll fill about 4,271 pages with the same value. When updating a row to set this column to an "ABC", I'm not sure how it impacts performance and concurrency. After we made it, we started getting strange locking problems later that day that we could not explain. I was called that night because a different index had become corrupt and had to be rebuilt. Although it wasn't the index we made, it was a composite index that had the same first column. Also the message said somthing like "key: too many parts or too long." Are my problems related to my index?? Could this cause corruption?? Thanks, Dave Killough