Solution to plsql connection failure: A blank prompt box is displayed.

Solution:
1. Run as administrator in win7

2. Modify the time zone

Files required (the first half may vary depending on the path of your installation ):
A: D: \ oracle \ product \ 10.2.0 \ db_1 \ WJLMGQS-PC_WJLMGQS \ sysman \ config \ emd. properties
B: D: \ oracle \ product \ 10.2.0 \ db_1 \ sysman \ config \ emd. properties
C: D: \ oracle \ product \ 10.2.0 \ db_1 \ sysman \ admin \ supportedtzs. lst

Specific operations:
A: Open the two emd. properties files, locate the last line of the file, and find that agentTZRegion = GMT
B: Open the supportedtzs. lst file, find the time zone you want to locate, and then select the parameter,
For example, agentTZRegion = Asia/Shanghai
Both methods have solved this problem.