============================================================================= AST RESEARCH, INC. TECHNICAL BULLETIN #0762 07-01-92 ============================================================================= AST 5251/11 ENHANCED AND PC GUARDIAN "VIRUS PREVENTION PLUS" PROBLEM: When using the application "Virus Prevention Plus" from PC Guardian Security Products, with AST 5251/11 Enhanced emulation software, any attempt to unload emulation from memory will result in a system lock-up. CAUSE: With "Virus Prevention Plus" resident in memory, AST 5251/11 Enhanced emulation will not unload correctly because its software interrupt vectors have been changed by the PC Guardian software. AFFECTED SYSTEMS: AST 5251/11 Enhanced SOLUTION: AST EPD Marketing has determined that this problem will not be fixed. The AST 5251/11 Enhanced emulation product is working as designed. To force emulation to unload after its software interrupt vectors have been changed may corrupt the interrupt vector chain and cause failures with other DOS applications. As a work around, AST recommends either not loading "Virus Prevention Plus" when using 5251/11 Enhanced emulation or rebooting the system to unload emulation.