SAS file references and file names have strict rules about what a valid SAS name can be. For example, this is a valid column or variable name: AGE_GROUP_1 however 1_AGE_GROUP is an invalid name because it starts with a number and SAS names cannot start with numbers. Valid SAS names can ONLY contain numbers, letters and underscores (spaces not allowed) and must start with a letter or underscore. So this would also be a valid variable or column name: _1_AGE_GROUP.
For example, as a name literal, it shows in the documentation that you could read in a column or variable with a name of [pre] '$ Amount Budgeted'n or 'Amount Spent'n [/pre] Note that in this syntax construction the whole string is quoted and is immediately followed by an n, which indicates that the string is a name literal.
You might want to open a track with Tech Support for more thorough help on this issue, they can look at all your code and your operating system configuration and make specific recommendations.