Packed:W32/MysticCompressor.gen!A is a Generic Detection for a packer called "Mystic Compressor", which is commonly used by the ZBot/Zeus trojan (password stealer programs) and rogue antispyware programs (such as XPAntivirus).
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.
Malware authors use packers, or file compressor programs, to compress their malware and thwart security programs attempting to scan, debug, emulate or unpack the compressed file as part of their normal security procedures.