This error occurs when trying to add feature classes from an ArcInfo coverage:
Open Failed Error opening feature class
There is at least one item or redefined item in one of the coverage feature attribute tables that is supported in INFO only, not in Arc.
Solution or Workaround
Locate the unsupported items in Workstation ArcInfo.
1. Start ArcInfo and navigate to the workspace where your data resides.
2. Type DIRECTORY INFO <COVERAGE_NAME>.* to list all of the INFO tables for your coverage.
3. Type ITEMS <INFO_FILE_NAME> to list the item definitions for an INFO file. Look under the TYPE column heading. ¤ Item types B, C, D, F, I, and N are supported in ArcInfo. ¤ Item types L, O, P, T, and V are supported in INFO only.
Use the ALTER command in INFO to change the definition of the item to a supported type.
1. Start INFO by typing INFO at the Arc: prompt.
2. Select the INFO file by using SELECT <INFO_FILE_NAME>.
3. List the INFO file item information using ITEMS.
4. Type ALTER: a. Enter the item name. b. Enter an alternate item name. c. Enter the new starting column. d. Enter the item width. e. Enter the output width. f. Enter a supported item type. g. Fill in new items for the remainder of the ALTER prompts. Press the Enter to keep the same value.