Rapidly using different Spells sometimes displays no visual indication while casting

Platform: Windows Vista x64 Ultimate
ISP: Alice (german)
Type of Internet Connection: DSL
Internet Connection Speed: 16Mbit/s
Date & Time: 13:30 (GMT+2)
Frequency: Sometimes
Character Name: Rhya Neema
Race: Mi'quote F
World: Wutai
Class/Skill Rank: Conjurer 50
Physical Level: None
Area and Coordinates: Western Thanalan @11-25
Party or Solo: Party
NPC Name: None
Monster Name: Nest Commander
In-Game Time: unknown

Steps:
1. Start Final Fantasy XIV
2. Select a Chracter who has multiple spells
3. Engage any monster
4. Cast One of the spells
5. Cast Another spell
6. Repeat steps 4 and 5 until the issue occurs

Results:

The spell is being cast but the character remains in his idle animation and the Casting gauge does not show up. The character only changes poses when the spell is being cast at that time a full Casting gauge is shown as well.

Expected Result:

The casting gauge and animation should always show when a character begins casting a spell.

Greetings RhyaNeema!

Thanks for entering all the required details! We will gladly forward the concern to be looked into. I do apologize for any trouble or inconvenience it has been causing. If there are any updates throughout the investigation they may be posted within the forums. Thanks!